President George W. Bush has likened the "war on terrorism" to the cold war against communism.
Addressing military cadets graduating from West Point, Mr Bush reaffirmed at the weekend that the US "will not rest until the promise of liberty reaches every people in every nation".
But as the US struggles to assert itself on the international stage, the president's most radical supporters now dismiss this as mere rhetoric, and traditional conservatives are questioning the wisdom of a democratisation strategy that has brought unpleasant consequences in the Middle East.
Administration officials speak privately of a sense of fatigue over the worsening crisis in Iraq that has drained energy from other important policy issues. Senior officials are leaving - not so unusual in a second term, but still giving the sense of a sinking ship run in some quarters by relatively inexperienced crew.
Neo-conservative commentators at the American Enterprise Institute wrote last week what amounted to an obituary of the Bush freedom doctrine.
"Bush killed his own doctrine," they said, describing the final blow as the resumption of diplomatic relations with Libya. This betrayal of Libyan democracy activists, they said, came after the US watched Egypt abrogate elections, ignored the collapse of the "Cedar Revolution" in Lebanon, abandoned imprisoned Chinese dissidents and started considering a peace treaty with Stalinist North Korea.
The neo-conservatives offered no explanation for desertion of the doctrine, other than a desire to make quick but transitory short-term gains. "The president continues to believe his own preaching, but his administration has become incapable of making the hard choices those beliefs require," they wrote.
But the ranks of the neo-conservatives are also being depleted. In his new book, America at the Crossroads, Francis Fukuyama, perhaps the movement's most outstanding intellectual force, confirms his defection from the brand concepts of "pre-emption, regime change, unilateralism and benevolent hegemony as put into practice by the Bush administration".
"It seems to me better to abandon the label and articulate an altogether distinct foreign policy position," he writes.
Advisers to the White House say it would be premature, however, to write off the doctrine of pre-emption, which was restated in the National Security Strategy released in March. But on Iran, for example, they believe the Bush administration is moving towards a cold war-style strategy of containment and deterrence with as broad an international coalition as possible.
Graham Fuller, former diplomat and intelligence officer, suggests the US is suffering from "strategic fatigue" brought on by "imperial over-reach".
"The administration's bark is minimised, and much of the bite seems gone," he writes in the Nixon Center's National Interest journal. "Has superpower fatigue set in? Clearly so, to judge by the administration's own dwindling energy and its sober acknowledgment that changing the face of the world is a lot tougher than it had hoped."
Short-term economic costs of the empire have been bearable, says Mr Fuller, but long-term indicators show it is not sustainable - massive domestic debt, growing trade imbalances, an extraordinary gap in wealth between rich and poor Americans, the growing outsourcing of jobs.
More immediately, the unprecedented unilateral character of the US exercise of global power has proved its undoing.
Condoleezza Rice, the secretary of state, has tried to redress this in Mr Bush's second term, but key allies - Britain's Tony Blair, for example - are also suffering from weakened credibility.
In contrast, Russia, which Mr Bush saw as a declining power when he came to office in 2001, is asserting itself on the international stage. So is China.
Neither wants to declare itself explicitly at odds with the US, but they share a common agenda and ability to stymie Washington's will. This is seen in their policies towards Iran, North Korea, Syria, the new Palestinian government led by Hamas, and Venezuela.
"In the last few years, diverse countries have deployed a multiplicity of strategies and tactics designed to weaken, divert, complicate, limit, delay or block the Bush agenda through a death by a thousand cuts," says Mr Fuller.
Even some traditional Republicans are challenging the concept that the global "war on terror" is the paramount issue for generations to come.
Richard Lugar, chairman of the Senate's powerful foreign relations committee, suggested that "there are a good many who would feel that the possibilities for devastation of countries, including our own, may come much more from our myopia in terms of energy policy than our ability to track down the last of the al-Qaeda cells".
Robert Jervis, professor of international politics at Columbia University, argues in the Washington Quarterly that the US system does not have the commitment to sustain the prolonged efforts required by Mr Bush's "transformationalist" agenda.
Copyright © 2006 The Financial Times Limited.