By Jon Leyne BBC correspondent in Washington

It is even listed as number 3 of 13 rules in his autobiography: "Avoid having your ego so close to your position that when your position falls, you ego goes with it."

But even Mr Powell allowed himself a glimmer of a smile when the United Nations Security Council passed its resolution on Iraq unanimously last week.

"O ye of little faith," was the gentle message.

Critics on both sides

And there have certainly been plenty of doubters of Mr Powell in the last few weeks, indeed throughout the 22 months he has been US Secretary of State.

That last bastion of American liberalism, the New York Times, even chided him for not threatening to resign when he seemed not to be getting his way over the summer.

Powell persuaded Bush to involve the UN in the campaign against Iraq

In fact Mr Powell joked at a recent dinner in New York about being criticised from both the left and the right.

He said he had discussed it with President Bush in the Oval Office.

"I said, 'Mr President I don't know how to handle it. It's so hard. The New York Times wants me to quit, the Washington Times wants you to fire me'."

The Washington Times is as right wing as the New York Times is left wing.

"And he said, 'Colin, that's right where I want you to be.'"

Presidential approval

The audience in New York liked that. But recently the secretary of state has been having the last laugh.

In fact the reason Mr Powell could be so jocular at such a critical moment is now becoming apparent.

Because just at the moment he seemed to be losing the battle within this deeply divided administration, Colin Powell actually had the president on his side.

The right wingers are circling, waiting to make sure the UN does not go soft on Iraq

According to sources in Washington, it was as early as 5 August that Mr Powell persuaded President Bush of the need to engage the UN in the campaign against Iraq.

To the dismay of those accompanying the Secretary of State on a round the world trip, he cancelled a final stopover in Hawaii.

What the journalists with him did not realise is that he had been summoned to a private dinner at the White House the following night.

And despite just returning from such a gruelling trip, Mr Powell used that occasion to persuade Mr Bush of the merits of working with the UN.

Battles to come

It was not until last Friday that the benefits of that decision finally became apparent.

The US has won international, and domestic, support for its policy on Iraq, without sacrificing any significant freedom of manoeuvre.

The UN resolution says Saddam must comply with the weapons inspectors

But if there is one lesson in this administration, it is that ceasefire lines in the ideological battle do not hold for long.

The right wingers, Vice-President Dick Cheney, Defence Secretary Donald Rumsfeld and his deputy Paul Wolfowitz, are circling, waiting to make sure the UN does not go soft on Iraq.

They could still be proved right. It could yet be that Saddam Hussein succeeds in subtly dividing a wedge between the members of the Security Council, delaying or perhaps even preventing the war the administration ideologues seem to yearn for.

The next big test will be Iraq's declaration on 8 December. By that date, the Security Council has demanded that Saddam Hussein make a full inventory of his weapons of mass destruction.

It is time to come clean. If he doesn't, the Americans could well move, straight away, to declare Iraq in material breach of its obligations - and that's a short step from war.

But for the moment Colin Powell is in the ascendant. And that means that if and when the time comes for war, there will be one more round of coalition building, with the secretary of state at the head.