While the US Congress and the White House continue to be absorbed with the latest video clips in the Monica Lewinsky affair, world leaders are beginning to worry that the most enduring effect of the scandal will be a complete absence of American action in international affairs.

Seldom before has this US influence been more urgently needed. For the first time since the end of the Cold War the basic premises of a world order are challenged. And, without decisive action from Washington, little can be done.

Bill Clinton has spent the last few weeks reassuring everyone that he remains in complete control over events. Indeed, earlier this week the White House deliberately choreographed a meeting between the President and his national security advisers in order to emphasise that, although Congress may be interested in the minutiae of sexual titillation, the commander-in-chief has higher priorities on his mind.

To a certain extent, the claim carries some credibility. The US constitution virtually decrees regular periods of political paralysis in Washington, especially during congressional elections and the handover stage between an incoming and outgoing presidency. The machinery of state continues, however, and Washington was not prevented from intervening in various international crises in the past.

It is usually forgotten that President Clinton committed troops to Bosnia in 1996, an election year, and, if conventional wisdom is to be believed, hardly the most appropriate moment for taking military risks. Furthermore, there is a consensus on foreign policy issues, even when Congress suspects that the President may be engaging in international adventures in order to deflect attention from his difficulties at home.

The reaction of the Republicans on Capitol Hill to Clinton's decision to strike against Afghanistan and Sudan last month is but the latest indication of an unwritten American rule: there are no votes to be gained in criticising a president who has committed US troops overseas. And, finally, the US is the ultimate, and most perfect, world power: a country which combines economic superiority with military might.

The bureaucracy of such a state continues to function regardless of what happens in the White House; satellites continue to churn out intelligence material, and thousands of employees around Washington pore over its details. All these considerations are important. But they only tell part of the story.

For the reality is that, although the President has complete control over the armed forces of his country - and possibly actually an incentive to use them at this stage - most of the crises which are now engulfing the world require a more concerted action, which virtually decrees a close co-operation with Congress. And it is this which President Clinton has forfeited, probably for ever.

Asia now resembles Europe at the beginning of the century. It has countries which are experiencing a gradual decline, and states which are determined to translate their economic growth into military might. It is riddled with territorial disputes and, as in Europe a century ago, the absence of serious regional co-operation structures has led to a furious arms race and a growing competition for spheres of influence.

Averting these developments was one of President Clinton's chief foreign policy priorities, and it has ended in failure. Nor is the failure confined to Asia alone. The Palestinian-Israeli peace process is defunct, the dual policy of containing both Iraq and Iran at the same time cannot be sustained beyond this year, while stability in Russia - another Clinton objective - is now seriously threatened.

In Kosovo, the Americans are pursuing a policy which is designed to prevent violence but maintain Serb control, a strategy which cannot work. And throughout Africa, conflicts continue to range with alarming regularity. Washington cannot be held accountable for these developments.

But the country which, as late as 1991, was proclaiming a new "world order" in which American values of free markets, human rights and collective economic security triumphed, is now faced with a multipolar world in which its overwhelming military superiority is of little use and where the current financial crisis is discrediting the very idea of free markets.

The roots of the failure lie in the fact that the US itself never pursued its regional co-operation efforts with conviction. Americans encouraged Asia to develop security structures. But they also operated a separate policy towards Korea and China, and upgraded their bilateral military relationship with Japan.

Washington promoted the enlargement of the North Atlantic Treaty Organisation to the countries of central Europe. But they also retained their separate policy towards Russia and were keen to maintain their special relationship with both Germany and Britain.

In Latin America, Clinton offered free trade. But he also enticed Argentina with the status of a "strategic ally", while dangling to Brazil an offer of possible membership of the UN Security Council. The often contradictory nature of this policy bred confusion and resentment. India's main reason for its nuclear tests is to acquire regional superpower status on its own terms, rather than on the basis of those dictated by Washington.

Yet even if Clinton pursued a better strategy, the American political system was never designed to sustain a coherent foreign policy. The country spends a mere 1 per cent of its budget on foreign aid, with only a tiny amount allocated to Africa, and even this is now conditioned on ridiculous anti-abortion policies.

The Republican-dominated Congress is still reluctant to increase support for the International Monetary Fund or eliminate the debt which the US owes to the United Nations. And Congress may grow even more opposed to any demands to spend American money on saving bankrupt economies around the world, the most urgent task facing Washington at the moment.

Presidents in the last two years of their mandate tend to concentrate on foreign policy issues, since these are virtually the only topics on which they can make a difference. Clinton has gone down this road, by advocating financial rescue packages for Asia, Russia and Latin America. He also wants the US to make a more active contribution to international institutions.

But success on all these problems requires a head of state who enjoys moral authority at home and who, because he is serving the last years of his term, is no longer controversial in Congress. These are precisely the advantages which Clinton does not enjoy and is unlikely to recoup, almost regardless of how the current scandal develops.

A lame-duck presidency is therefore not only on the cards, but virtually inevitable.

Jonathan Eyal is director of studies at the Royal United Services Institute in London