During a joint press conference in Washington the two men, with an almost introspective quality to their answers, conceded how murderous and difficult the Iraq war had become.

Mr Bush said he regretted his cowboy rhetoric, specifically his challenge to Iraqi insurgents early in the armed uprising to "bring it on". He also said the Abu Ghraib prison abuse scandal had been greatly damaged his attempts to bring democracy to Iraq.

"I said some things that were misinterpreted and I learned from that," Mr Bush said.

The Prime Minister appeared with Mr Bush as the two men, trying to fend of the allegations that they are lame duck leaders in the late autumn of their political careers, look to shape their legacies and justify the invasion of Iraq.

Both Mr Blair and Mr Bush conceded that the Iraq war had taken a heavy toll on their political standing, but the Prime Minister, fresh from a visit to Baghdad this week, insisted: "For all the hardships and challenges in the past few years I shall think that it was a cause worth fighting for."

Mr Blair said that Nouri al-Maliki’s Government had made it clear when he visited Iraq this week that it wants coalition troops to remain at least in the shortterm. But he also left open the possibility that coalition troops could be out of Iraq within 18 months.

Mr Blair, ahead of a speech today in which he hopes to restore his reputation as a believer in multilateral solutions to international problems, told world leaders that they had a duty to unite behind the new Iraqi government, despite the "deeply divisive and controversial" decision by Britain and the US to begin the war.

He conceded that the last three years in Iraq had been filled with bloodshed and violence, but said "it is our duty and the whole of the international
community to get behind the Iraqi government and support it." He added that he was "more certain than ever" that the new Iraqi government must know the international community stands with it.

His visit to Washington comes against a backdrop of failure and frustration within multilateral organisations on international trade talks, the Middle East peace protest and possible UN sanctions on Iran.

However, he will set out specific proposals in his speech to reinvigorate the UN, the International Monetary Fund, the World Bank and the G8 among others so that they meet the global challenges of the 21st century. This, he will say today, means making them more transparent and representative, and better able “to take on hard issues” such as Iraq.

The Bush Administration, in particular, has been sceptical about international deals on issues such as climate change and the Middle East.
The Prime Minister is expected to say today: “Acting multilaterally should always be our preference. Big countries fought not to duck big issues and make them worse.”

Downing Street believes that this is a good time to “test the water” in America on climate change because rising oil prices and fears about the security of supply have served to “concentrate the minds” of the US Administration.

Although there is little prospect of Mr Bush signing up to the Kyoto protocol which sets targets for cuts in greenhouse gas emissions, it the US is interested in practical measures such as promoting the use of new technologies that produce less carbon dioxide.

The World Bank, the International Monetary Fund and the UN were all set up in 1945 primarily with the interests of America, Japan and Europe in mind. Mr Blair will say that globalisation has made the world a very different and much more interdependent place than it was 60 years ago.

In his speech Mr Blair will echo recent remarks by Gordon Brown who has called for the IMF to “focus more on crisis prevention as well as crisis resolution” by extending its monitoring role to developing economies.

Mr Blair, in words that will not be welcomed by Gordon Brown, said he would like to see Mr Blair remain in office until he leaves the White House - in January 2009.

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