The military victory in Iraq seems to have confirmed a new world order. Not since Rome has one nation loomed so large above the others. Indeed the word "empire" has come out of the closet. Respected analysts of both left and right are beginning to refer to "American empire" approvingly as the dominant narrative of the 21st century.

But those who openly welcome the idea of an American empire mistake the underlying nature of American public opinion. Neoconservatives such as Max Boot argue that the United States should provide troubled countries with the sort of enlightened foreign administration once provided by self-confident Englishmen in jodhpurs and pith helmets.

Some say the United States is already an empire and it is just a matter of recognizing reality. It's a mistake, however, to confuse the politics of primacy with those of empire. The United States is more powerful compared with other countries than Britain was at its imperial peak, but it has less control over what occurs inside other countries than Britain did when it ruled a quarter of the globe. For example, Kenya's schools, taxes, laws and elections -- not to mention external relations -- were controlled by British officials. The United States has no such control today. We could not even get the votes of Mexico and Chile for a second UN Security Council resolution. Devotees of the new imperialism say not to be so literal. "Empire" is merely a metaphor. But the problem with the metaphor is that it implies a control from Washington that is unrealistic and reinforces the prevailing strong temptations toward unilateralism.

Despite its natal ideology of anti-imperialism, the United States has intervened and governed countries in Central America and the Caribbean as well as the Philippines. But imperialism has never been a comfortable experience for Americans, and only a small portion of the cases led directly to the establishment of democracies. American empire is not limited by "imperial overstretch" in the sense of costing an impossible portion of our gross national product. We devoted a much higher percentage of GNP to the military budget during the Cold War than we do today. The overstretch will come from having to police more and more peripheral countries -- more than public opinion will accept. Polls show little popular taste for empire.

In fact, the problem of creating an American empire might better be termed imperial understretch. Neither the public nor Congress has proved willing to invest seriously in the instruments of nation-building and governance as opposed to military force. The entire budget of the State Department and the U.S. Agency for International Development is only about 1 percent of the federal budget. The United States spends nearly 16 times as much on its military, and there is little indication that this is about to change in an era of tax cuts and budget deficits. Our military is designed for fighting rather than police work. The administration has cut back on training for peacekeeping operations. It tends to eschew nation-building and has designed a military that is better suited to kick down the door, beat up a dictator and then go home, rather than stay for the harder work of building a democratic polity.

Consider the following three scenarios among the large number of possible futures for Iraq. The first is a 1945 Germany-Japan scenario in which the United States stays for seven years and leaves behind a friendly democracy. That is the preferred outcome, but it is worth remembering that Germany and Japan were ethnically homogeneous societies with significant middle classes that had experienced democracy in the 1920s, and in which there were no terrorist responses to the presence of U.S. troops.

A second scenario is President Ronald Reagan in Lebanon. Some of the people who cheered our entry wind up protesting our presence. Terrorists kill U.S. soldiers, and the public reacts by saying, "Saddam Hussein and the weapons are gone, they don't want our democracy, let's pull out."

Third is a Bosnia-Kosovo scenario in which the United States entices NATO allies and others to help in the policing and reconstruction of Iraq. A UN resolution would bless the force, and an international administrator would help legitimize decisions. The process would be long and frustrating but would reduce the prominence of the United States as a target for anti-imperialists and probably provide the best prospect that the United States would not pull out prematurely. Ironically, the neoconservative strand of the administration might have to make common cause with the multilateral realists to achieve its objectives. It might find that the world's only superpower is not suited for empire after all.

Joseph S. Nye is dean of Harvard University's Kennedy School of Government and author of "The Paradox of American Power." He contributed this comment to The Washington Post.