Like an aristocrat in reduced circumstances, Francis Fukuyama carries around a title that is a source of both prestige and ridicule. The title belongs to his most notorious work, The End of History (1992). To be fair, the thesis that it describes is considerably wiser and more interesting than the title suggests, and Gramscian rather than Leninist in the style of its liberal capitalist teleology.

When The End of History was published, Fukuyama's views fitted perfectly with the general triumphalism that followed the end of the cold war. Now he has managed once again to insert himself into the American zeitgeist, but a very different one. His latest book displays no triumphalism, but chimes equally well with the growing sense of unease in America about where the Bush administration's reckless policies are leading the country. These are policies that Fukuyama formerly supported, but has since publicly disowned.

George W Bush is currently facing the lowest public approval ratings of his presidency. According to recent polls, Americans want a Democrat-controlled Congress, as opposed to a Republican one, by a margin of 50 to 37 per cent; 67 per cent of Americans think that the Iraq war "was not necessary for the defence of the United States"; and 59 per cent believe that US resources would have been better used to pursue al-Qaeda and help Afghanistan.

Confronted with such figures, the propaganda bulwarks of the Bush administration have, in recent months, often vanished from view behind the mass of intellectuals and journalists try- ing to jump off them. A rabble of former public advocates of war in Iraq has belatedly condemned the US government for how that war has been conducted. In what the American Prospect has rightly termed "the incompetence dodge", they have explained that they could not have been expected to know how badly the Bush administration and the US military would carry out the brilliant strategy for which they had argued so shrilly in the run-up to war.

Another tactic has been to blame the war exclusively on the neoconservatives, as if it had not been supported by numerous public figures - Democrats as well as Republicans - from outside that movement. In fact, some of the harshest and most unscrupulous advocacy of the war came from intellectuals attached to the leadership of the Democratic Party. None the less, the charge against the neocons is fair enough in itself and, given the way things are going in Iraq, seems likely to sink them not just in the eyes of history but also, much more importantly (from the perspective of would-be intellectual apparatchiks), in the eyes of future government employers.

To be fair to Fukuyama, if he was among the first to call for war in Iraq, he was also among the first to jump ship. He advocated the overthrow of Saddam Hussein both before and immediately after 9/11, but as war approached he became increasingly worried. Before the 2004 elections he declared that, in view of Bush's record, he would not vote for him again as president.

Today, Fukuyama clearly hopes to play a leading role in shaping a new US foreign-policy consensus in the remaining years of Bush's lame-duck presidency and the agonisingly slow run-up to the next presidential elections. To that end, he has been instrumental in helping set up a new foreign-policy magazine, the American Interest.

In After the Neocons, based on lectures given at Yale University last year, Fukuyama formally breaks with the present neocon- servative grouping, though not wholly with the neoconservative tradition: "I have concluded that neoconservatism, as both a political symbol and a body of thought, has evolved into something that I can no longer support . . . rather than attempting the feckless task of reclaiming the term, it seems to me better to abandon the label and articulate an altogether distinct foreign-policy position."

Fukuyama's new book, as well as his claim to shape US foreign policy, therefore stands or falls by the answers to two linked questions. First, has he really broken with neoconservative thought or has he only cast off a "label" that has become politically inconvenient? Second, has he really crafted a foreign-policy position that is not only "altogether distinct" from that of the neoconservatives but offers something genuinely new and useful to the US debate?

The answer to the first question is that Fukuyama has significantly broken with the neocons. Although he continues to argue for "the use of American power to achieve moral purposes", his arguments also now contain traditional conservative elements - scepticism, stewardship, prudence - that have been absent from the neoconservative lexicon, at least since the end of the cold war.

Fukuyama strongly criticises the unreal expectations and the lack of knowledge and research that led to the dreadful failures of analysis and planning in Iraq. He makes a number of highly cogent criticisms of weaknesses that have in recent years affected the thinking not merely of neoconservatives, but of the US establishment as a whole.

Among these is what he calls the "universalisation of the experience of the east Europeans [during and after the collapse of the Soviet empire] to other parts of the world". This outlook ignores the unique circumstances that made possible the east European combination of rapid democratisation, successful economic reform and pro-US foreign policy.

Fukuyama also makes one very useful recommendation, in an area that has once again been neglected by the US establishment. This is the need to accompany attempts at spreading democracy with a vastly greater commitment to international development. As Fukuyama rightly says, development policy needs to be directed not only at strengthening economies, but also at building up the state institutions that are necessary for stable economic growth to take place and for democracies to take root in the long term. He calls this "realistic Wilsonianism".

All of this is eminently sensible, and indeed - if I may say so with what I hope is pardonable bitterness - many have been arguing these positions for considerably longer than Fukuyama. But when it comes to crafting a new US foreign policy, his work suffers from a severe disability - one that affects all too many American commentators.

This is its lack of detail concerning controversial questions. Fukuyama wisely advocates a limited, "Bismarckian" approach to the exercise of US power. But what does that mean in practice when it comes to the defence of Taiwan, the expansion of Nato into the former Soviet Union and a choice of war or détente with Iran? Above all, what settlement does he advocate for the Israeli-Palestinian conflict?

Fukuyama has a powerful intellect, and has been responsible for some interesting and valuable contributions to contemporary thought, especially concerning the origins and conditions of economic development. But until he and other leading public figures in the US are prepared to take tough and unpopular stands on critical issues, all the intellectual brilliance in the world won't save their country from sliding into one disaster after another.

Anatol Lieven is a senior research fellow at the New America Foundation in Washington, DC. His latest book, America Right or Wrong: an anatomy of American nationalism, is published by HarperCollins