Tony Blair arrived in Washington yesterday, knowing that the next time he sets foot in the US capital he may well be speaking to an audience of corporate suits on the public-speaking circuit for former politicians.

In Britain attention is already switching to Gordon Brown and yesterday the only questions that Downing Street faced at its morning briefing on the Washington visit were about whether writers of valedictory profiles were accompanying Mr Blair. But No 10 maintains that the two-day visit to see President Bush is “not just to say farewell” and that the two leaders will discuss serious issues such as trade deals, Iraq, Iran and climate change.

Mr Blair’s trip includes at least one event that appears to be more about his legacy than what he might achieve in his final days in office. He will attend a reception at the British Embassy this evening to thank the many Americans who have helped him with the Northern Ireland peace process. Although he is still treated with far more respect in the US than he receives at home — with few commentators doubting that he went to war in Iraq for good motives — on both sides of the Atlantic there is agreement that his place in history will be as Mr Bush’s ally in that conflict.

In an NBC interview broadcast here on Tuesday night, Mr Blair insisted that his support for the war was never based on the notion that “well, America wants it, that’s what we’ve got to do”. Instead, he said: “I believe that September 11th was an attack on all of us. And my own view now, today, is even clearer than it was back then.” Would he do it again? “I would make the same decision to remove Saddam, yes.”

As The Times reported yesterday, Mr Blair hopes to secure Mr Bush’s backing for proposals being tabled at next month’s meeting of G8 leaders on tackling global warming. In Washington there are already hints that the Prime Minister’s reach may once again be exceeding his grasp.

The Bush Administration has signalled that it remains opposed to binding targets on cutting greenhouse gas emissions and limiting the rise on temperature, while having “strong reservations” about a European scheme for a global “cap and trade” on carbon-burning permits.

Mr Blair was praised last week by Mr Bush as man a whose word “you can take to the bank”. The Prime Minister returned the compliment, saying: “I’ve found him immensely straightforward to deal with, someone always true to his word and someone who’s a very strong leader.” He added: “I know sometimes people kind of prompt me and say, ‘Well, do you really think this?’ and the answer is, ‘I do’.”

What he described as the “intense criticism” over that alliance explains why his successor as prime minister will be wary of getting too close to Mr Bush or possibly any American president. Although Mr Brown is expected to make an early visit to Washington when he takes over, his “chance encounter” with the President last month — when he was here for the annual World Bank and IMF meetings — was carefully arranged so that it was out of sight of cameras.

David Cameron, the Conservative leader, whose speech on the anniversary of 9/11 last year has been seen widely as an attack on Mr Bush, is understood to be reluctant to come to Washington at all until there is a change of president.

No Tory leader has set foot in the US capital in almost five years, the longest such absence since the advent of jet travel.

Rightwingers in Washington are now well aware of this apparent snub. John Bolton, the former US Ambassador to the United Nations, told The Times: “I say to all my friends in the Conservative Party that they need to be very careful about the course Cameron is following — Republicans are watching this very closely.”

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