The fierce debate on immigration ignores a crucial reality -- what is happening to the United States is only one piece, although a big one, of a much larger global picture.

That hit me a couple of weeks ago when I was in Singapore. The Southeast Asian island nation has long been hailed as an economic model, the business capital for the entire region.

But it is an economy facing demographic peril. Its small population of 4 million is shrinking, thanks to a very low fertility rate. Prosperous Singaporean couples work hard, have fewer children and worry about how to take care of their aging parents. By 2050, Singapore will have a median age of over 52, one of the oldest in the world.

Singapore's answer is to import labor. A third of its workforce are migrants, from construction workers to maids. One out of seven households employs a domestic worker -- low-paid women mostly from neighboring Philippines and Indonesia.

Singapore tries to lure "talents'' -- highly skilled and affluent migrants -- to stay permanently. But the men hauling bricks and the maids washing laundry are in a separate class of temporary guest workers, with no chance to join Singaporean society. If a maid becomes pregnant, she is shipped out within seven days. Employers have to post bonds that must be paid should their servants break the rules and try to stay, putting them in the role of migrant police.

Problems of abuse of domestic workers, including physical and sexual violence and confinement, are serious enough to have prompted a report last December by Human Rights Watch.

Singapore's dependence on migrant labor and its guest-worker policy may be at the extreme end but it's very much on the global spectrum. Labor, like capital and goods before it, is part of a global market. The movement of people across borders in search of wages and work, most of it from developing countries to developed, is growing at a phenomenal pace.

The numbers are staggering. From 1980 to 2000, the number of migrants living in the developed world more than doubled from 48 million to 110 million. Migrants make up an average 12 percent of the workforce in high-income countries. About 4 million migrants cross borders illegally every year.

The demand for labor is driven in part by a demographic disaster -- the falling birth rates of developed countries. Almost all of those countries now have fertility rates that are well below 2.1, the level at which a population replaces itself. At the very low end are Hong Kong (0.94), Korea (1.22) and Singapore in Asia (1.24), along with much of Eastern Europe.

Low fertility means shrinking workforces and aging populations. Without migration, according to a recent study, Europe's population would have declined by 4.4 million from 1995 to 2000. Immigration accounted for 75 percent of U.S. population growth during the same period.

This movement of people cannot be stopped, certainly not by hundreds of miles of fences or even by tens of thousands of border guards. It is an issue that cries out for global cooperation, for common policies that cut across national boundaries. Already, we can benefit from looking at what has worked -- and not worked -- elsewhere.

A Global Commission on International Migration, formed in 2003 by the United Nations secretary-general, has taken an initial stab. Their report, issued last winter, supports the growth of guest-worker programs.

The Senate immigration bill now up for debate includes a provision for a guest-worker program. The bill is clearly preferable to the punitive and ineffective approach of the House version. But the Singapore experience -- and previous guest-worker programs like the German import of Turks -- should prompt second thoughts about going down this road.

One problem is that the guests don't leave. The United States has its own experience with this in the bracero program to import farmworkers, and more recently with the supposedly temporary H1-B visas used so extensively by the high-tech industry here in Silicon Valley.

Most troubling to me, these programs create an underclass of migrants who are never assimilated, as happened in Germany. It sets us on the Singapore road, encouraging inhumane policing mechanisms. And it is a gilded invitation to employers to depress the wages and incomes of American workers, and not just in the dirty jobs that are supposedly so hard to fill.

The United States has been rightfully proud of a tradition that treats all immigrants as citizens in the making. Rather than guest workers, isn't it more American to set realistic immigration quotas and enforce them fairly?

Joseph S. Nye, the Dean Emeritus of Harvard's Kennedy School of Government, the Sultan of Oman Professor of International Relations, and a member of the Board of Harvard's Center for Science and International Affairs, has been selected to deliver the second annual S.T. Lee lecture. The lectureship, established by Dr. Seng Tee Lee of Singapore, enables the Institute to invite a distinguished scholar to deliver an annual lecture on international political, social or health issues.

Nye is the author of numerous books and articles on major global issues and challenges. A world renowned expert on the use of "soft" and "hard" power in international political, economic, and security affairs, Nye captured global attention with his 2004 book, Soft Power: the Means to Success in World Politics (New York, NY: Public Affairs), and continues to offer arresting insights and perspective in lectures around the world.

This week President Bush will seek to focus the nation's attention on border security and immigration reform. But the president's proposals won't protect Americans from our gravest cross-border threat: the possibility that a ship, truck or train will one day import a 40-foot cargo container in which terrorists have hidden a dirty bomb or nuclear weapon.

The Bush administration maintains that it has a smart strategy to reduce this risk. A new 24-Hour Rule requires that importers report the contents of their containers to customs inspectors one day before the boxes are loaded on ships bound for the United States. The Department of Homeland Security's National Targeting Center then reviews the data, checking against other intelligence to determine which boxes may pose a threat. Although the containers deemed high risk are inspected at cooperating foreign ports or when they enter the United States, the rest--more than 90 percent--land here without any perusal.

We have two concerns about this strategy. First, it presumes that the United States government has good enough intelligence about Al Qaeda to reliably discern which containers are suspicious and which are not. But our inability to thwart the attacks in Iraq demonstrates that we lack such specific tactical intelligence. And supporting customs inspectors, who must make the first assessment of risk, is not a priority for the intelligence agencies. Inspectors must rely on their experience in spotting anomalies--a company that claims to be exporting pineapples from Iceland, for example.

Second, determined terrorists can easily take advantage of the knowledge that customs inspectors routinely designate certain shipments as low risk. A container frequently makes 10 or more stops between its factory of origin and the vessel carrying it to American shores. Many of the way stations are in poorly policed parts of the world. Because name-brand companies like Wal-Mart and General Motors are widely known to be considered low-risk, terrorists need only to stake out their shipment routes and exploit the weakest points to introduce a weapon of mass destruction. A terrorist cell posing as a legal shipping company for more than two years, or a terrorist truck driver hauling goods from a well-known shipper, can also be confident of being perceived as low risk.

So what needs to be done? A pilot project under way in Hong Kong, the world's largest container port along with Singapore, offers one piece of a potential solution. At an estimated cost of $7 per container, new technology can photograph the box's exterior, screen for radioactive material, and collect a gamma-ray image of a box's contents while the truck on which it is carried moves at 10 miles per hour.

Terrorists can defeat radiation sensors by shielding a dirty bomb with dense materials like lead. But by combining those sensors with gamma ray images, the Hong Kong system allows inspectors to sound the alarm on suspiciously dense objects. Inspectors would need to analyze enough of the scans--perhaps 20 percent to 30 percent--to convince terrorists that there is a good chance that an indistinct image will lead a container's contents to be sent for more reliable X-ray or manual examinations. Images of container contents would then be reviewed remotely by inspectors inside the United States who are trained to spot possible nuclear weapons.

If terrorists were to succeed in shipping a dirty bomb, for example, the database of these images could serve as a kind of black box--an invaluable forensic tool in the effort to identify how and where security was breached. That information could help prevent politicians from reacting spasmodically and freezing the entire container system after an attack.

Such a program could significantly reduce the likelihood that terrorists will smuggle plutonium or a dirty bomb through American ports. But it still would not stop a terrorist from importing highly enriched uranium, which can be used to construct a nuclear weapon. Lengthening the time that a container is screened for radiation would help, and this could be done without increasing waiting times if additional monitors were added to the Hong Kong system near the gate where the trucks must already stop for driver identification checks. Better still would be for the Department of Homeland Security to make the development of new technology that can recognize the unique signature of highly enriched uranium an urgent priority.

Finally, we must find ways to ensure that terrorists do not breach containers before shipments arrive at loading ports. Sensors should be installed inside containers in order to track their movements, detect any infiltration and discern the presence of radioactive material. Where boxes are loaded, certified independent inspectors should verify that companies have followed adequate protocols to ensure that legitimate and authorized goods are being shipped.

Taken together, these recommendations will require new investments and an extraordinary degree of international cooperation. But increased container security will not only help the United States prevent terrorism, it will also help all countries reduce theft, stop the smuggling of drugs and humans, crack down on tariff evasion and improve export controls. What's more, such a program would require an investment of just one one-hundredth of the capital that could be lost if we shut down the global container shipping system after an attack.

Container security is a complex problem with enormous stakes. American officials insist that existing programs have matters well in hand. But we cannot afford to take these perky reassurances at face value while the same officials fail to embrace promising initiatives like the Hong Kong pilot project.

On the surface, President Bush's week-long swing through Northeast Asia has been a strong contrast with his recent stormy (and, some say, stumbling) excursion into Latin America.

There was little sign of overt anti-Americanism. And no Asian leader will openly oppose American leadership in the flamboyant manner of Venezuela's Hugo Chavez. Even prickly China swallowed President Bush's barbs about lack of democratic freedom in China, quietly acknowledging the two powers' differences. In contrast to the meeting of leaders from the Americas, the annual summit of the Asia Pacific Economic Cooperation (APEC) forum in Korea will embrace the principles of free trade.

Beneath the polite appearance, however, there is no less a challenge to American leadership in Asia. While Washington fiddled, a powerful momentum has been building up in Asia toward the formation of an East Asian Free Trade Area or, more ambitiously, an East Asian Community, modeled on the European community. Led by China, the East Asian grouping pointedly excludes the United States.

The APEC agenda focuses on an initiative to counter the spread of avian flu and to offer a common push at the WTO meeting in Hong Kong next month to revive the Doha Round of global trade talks. The Bush administration has its own agenda for the APEC meeting: to reposition itself as a leader of economic growth and integration in the region. For this, APEC has the virtue of being a more open organization than those behind the disappointment at the American summit. Its 21 members span the Pacific Rim, bringing together nations from Chile and Mexico to Russia, China and Southeast Asia. But this attention to APEC may be a case of too little, too late. The momentum to give the amorphous APEC an ongoing institutional role, beyond its annual summit meetings, has slowed in recent years. Its pledges for mutual tariff reduction exist almost entirely on paper.

Until this year, the Bush administration barely addressed regional economic issues at APEC. It preferred to use the meetings to promote a post-9/11 security agenda of anti-terrorism. U.S. trade policy has focused more on reaching free trade agreements with a few selected "friends" in that war, such as Singapore and Australia.

Meanwhile a Chinese-sponsored move to hold an East Asian summit offers the most visible expression of a trend of declining American influence in Asia. That meeting will take place in Malaysia in mid-December. The gathering groups the 10-member Association of Southeast Asian Nations, Japan, China, South Korea, India, Australia and New Zealand. Pointedly not invited is the United States.

This meeting is an outgrowth of the ASEAN Plus Three (APT) process - an annual dialogue of ASEAN with China, South Korea and Japan that began in December 1997 in the midst of the Asian financial crisis. The APT has grown into an elaborate mechanism for cooperation in a range of areas from finance and agriculture to information technology. This reflects an underlying economic reality - the growth of regional and bilateral trade agreements and the rapid rise of intra-Asian trade.

Until fairly recently, foreign trade in East Asia was dominated by trans-Pacific trade with the United States. But the share of Asian exports headed to the U.S. has dropped dramatically, while those destined for other Asian nations has risen. In the two decades from 1981 to 2001, according to economist Edward Lincoln, the share of intra-regional exports has risen from 32 percent to 40 percent, and intra-regional imports from 32 percent to 50 percent.

Much of the growth of regional integration is being driven by China, which is generating enormous demand for imports of raw materials as well as for semi-finished goods that are assembled for export. China has not been hesitant to use this role to expand its influence in the region. It has embraced the APT as a road towards creation of an East Asian community. At the ASEAN summit last year, Chinese Premier Wen Jiabao declared that such a community was a "long-term strategic choice in the interests of China's development." China has also outmatched the U.S. in negotiating free trade agreements, both bilateral and regional. The most impressive is an FTA deal between China and ASEAN set to take effect in 2010. Beijing even dreams of an Asian currency, based on the Chinese yuan, to rival the dollar and the euro.

China is not the first nation to try for such East Asian economic unity. Back in the days when Japan was riding high as an economic superpower, it too talked of leading an East Asian bloc, based on a yen currency zone. As late as 1997, in response to the Asian financial crisis, Japan proposed the creation of an Asian Monetary Fund, a kind of alternate regional financial system. More recently, both South Korea and Japan offered their own visions of an East Asian community in 2001. And both countries tried to match China in the APT by offering to form free trade agreements with ASEAN.

Japan, however, was never as successful as China is likely to be. "It would seem that Japan is a natural counterweight to China, but Tokyo is generally perceived as reactive and incapable of outflanking Beijing," Brad Glosserman, director of research at the Pacific Forum of CSIS, wrote recently. "Its economic dynamism is no match for that of China."

The United States has never been friendly toward efforts to create an East Asian economic bloc, viewing them as chipping away at the global trading system and rivaling American leadership. But Asia is arguably only following in American footsteps -- witness the NAFTA deal with Canada and Mexico and the more recent trade pact with Central America.

Many American policymakers believe these developments are partly a product of the failure of the Bush administration to articulate - much less pursue - a strategy to engage East Asia.

"The United States has greater strategic interests in Asia now than it did in Europe before World War I or World War II,'' argued a recent report of the Grand Strategic Choices Working Group, co-chaired by John Hopkin's University's Francis Fukuyama and Princeton's G. John Ikenberry. "Thus," the report continued, "it is unfortunate that part of the problem, in East Asia in particular, is that America's relative lack of interest in tending to the region has caused some allies of the U.S. to doubt our resolve and question the value of resisting unfavorable developments alone."

The report echoes other policymakers in suggesting the U.S. form its own East Asian economic zone with Japan, South Korea and Australia."That's a non-starter,'' says Professor Vinod Aggarwal, director of Berkeley's APEC study center. "Nobody wants to be cut out of the China market."

Privately, Bush administration officials downplay the importance of the East Asian summit in December, pointing to the lack of any concrete agenda. The addition of India, Australia and New Zealand to the invitation list, along with Japan, should effectively counter any Chinese initiative, they believe.

But those countries also fear being left out of whatever may emerge from this process. They cannot afford to be left on the outside, looking in.

Ultimately, neither can the United States. The President's trip is a belated recognition of that fact. But to be more than a momentary gesture, the United States must give East Asia the consistent attention it deserves.