Rupert Cornwell: Is this the end of Pax Americana?

Over the past year or so, the limits of American power have been exposed

Iraq burns, Afghanistan boils, and a nuclear North Korea tests its missiles with impunity. Iran, meanwhile, mockingly plays on both chess boards simultaneously, refusing to give up its nuclear ambitions, while employing its Hizbollah surrogates to lure Israel into a new Middle East war. Truly, it is hard to know where to begin in the hunt for famous last words uttered in the past six years by the rulers in this imagined seat of global empire on the Potomac river where I live.

Do we start with George Bush, with his line "sometimes a show of force by one side can really clarify things" at his first National Security Council meeting on 30 January 2001? That nostrum of statecraft, after all of 10 days in power, was delivered to an alarmed Secretary of State Colin Powell, after the President had declared that it wasn't worth America continuing to waste time on the intractable Israeli-Palestinian conflict. Well, we've got the show of force right now. Clarification, alas, is quite another matter.

Or was it the remark of one of those unnamed senior officials, delivered to the author Ron Suskind a couple of years ago, when the hubris of this White House was at its zenith - to the effect that reality was not an objective condition, but whatever the administration decided it should be? Probably, though, the prize belongs to Dick Cheney. (Who else, you will ask.)

Making the case for war with Iraq in August 2002, the Vice-President waxed lyrical on the benefits of a successful invasion. "Extremists would have to rethink their strategy of jihad, moderates throughout the region would take heart, and our ability to advance the Israeli-Palestinian peace process would be enhanced." Today, each of those three assertions lies in ruins. Instead, in the "arc of instability" stretching from Afghanistan and Pakistan westwards to Palestine and Israel, there is a dreadful confluence of events. Madeleine Albright, Powell's predecessor as Secretary of State, has called the interlocking crises "perfect storm" in international affairs.

Their outcome cannot be predicted. But one lesson historians will surely draw is that over the past year or so, the limits of American power have been exposed. And perhaps our historians will grant this weekend a special place in the unfolding of the new world disorder.

Watching American television news these past few days, you would have had little inkling of the change. As the screen showed images of flames and smoke spilling from fuel depots at Beirut airport that had just been bombed by Israeli jets, the news presenters reverentially awaited a press briefing that had hastily been summoned by Condoleezza Rice in Germany, en route to the G8 summit in St Petersburg, which opens today.

The emperor's chief foreign policy adviser was about to speak and, we were led to believe, everyone would somehow come to heel. In fact, the best she could come up with was an appeal for restraint by all sides. This was America speaking - but it might have been Portugal, South Africa or Argentina for all the difference it made.

And so to the G8. Leave aside for a moment that the great new world powers China and India are not there. These minutely choreographed, bureaucracy-encrusted events are at least meant to allow a "steering committee" of world leaders the chance to mull over the underlying issues of the day - in this case, global warming, the plight of the poorest countries, and how to contain the spread of weapons of mass destruction to Iran, North Korea and the like. Yet again, however, a G8 summit has been hijacked by an international crisis. It is hard to ponder abstractions when Beirut airport is ablaze and the Middle East is on the brink of meltdown.

In another way, this particular G8 is a symbol of the limits of American power. The summit seals the return of Russia as the power that cannot be ignored. Cheney may scold President Putin for squashing democracy at home and bullying neighbours abroad, while some ask what Russia, with an economy the size of the Netherlands (or is it Portugal?), is even doing at the table at all.

But Russia - not North Korea, al-Qa'ida or any other terrorist group - remains the sole power whose missiles can blow the US off the face of the earth. It has colossal reserves of oil and gas - imports of which have helped to turn the US into the greatest debtor nation in history. Moscow's agreement is essential for a diplomatic solution (which is to say the only solution) to the nuclear ambitions of Iran and North Korea. In short, America needs Russia a good deal more these days than Russia needs America.

And awareness of this changed state of affairs is growing even at the heart of the empire. Time magazine's cover proclaims "The End of Cowboy Diplomacy", while the man who sneered at the United Nations when he went to war in Iraq can hardly utter a sentence now that does not contain the word diplomacy. But we Europeans above all should contain our smugness at this new-found humility, at this belated and, it must be said, somewhat reluctant acknowledgement that America cannot go it alone.

The limits of Pax Americana may have been laid bare. But the very fact that we acquiesced in the notion is proof of how we depended on it. Safe in the knowledge that we had little impact on events, we could damn the US if it did, and we could damn it if it didn't. Pax Americana, like Pax Britannica and Pax Romana before it, might have been resented, but in many respects it made life for those who were subject to it a great deal easier.

In office, Madeleine Albright was fond of calling the US "the indispensable nation". She was right then and she is right now. Without US involvement no solution to major international problems is possible. Maybe no solution is possible at all, in which case we will move by default into a new era of competing power blocs.

But that, in a world interlinked and interdependent as never before, is surely a formula for disaster. The only way forward is for America's allies, foremost among them Europe, to add their weight to the hyperpower that cannot do it on its own. And thus we return to the familiar refrain. The Middle East burns, Iran threatens - but where, oh where, is Europe?