Britain has been asked formally by the Bush Administration to take Guantánamo terrorist suspects in an effort to close down the controversial detention centre in Cuba within weeks.

Robert Tuttle, the outgoing US Ambassador to London, told The Times yesterday that diplomatic efforts were at an advanced stage. He believes that countries such as Britain, which criticised Guantánamo, should be ready to help to close down the prison by taking some of its inmates.

The American envoy said in a farewell interview that the special relationship between London and Washington was still very strong, although he refused to say whether Gordon Brown would be the first foreign leader invited to the White House after Barack Obama is sworn in as President on January 20.

Much could depend on how Britain responds to Washington's efforts to relocate the 250 prisoners being held at Guantánamo Bay. The most serious al-Qaeda terror suspects are expected to be put on trial in the mainland United States, leaving dozens of inmates who are not regarded as a threat but have nowhere to go. “The Bush Administration has made a number of attempts - some successful, some not successful - to get other countries to take these remaining detainees,” Mr Tuttle said. “I am hopeful that some will be taken before January 20 and hopefully some taken afterwards.”

Albania has taken some Chinese prisoners and Portugal has said that it is ready to take more. Australia rejected the request. Britain has indicated that it is prepared to consider taking prisoners case by case, though the proposal has caused a rift in Whitehall.

“I would hope that if the UK could see its way through to take some detainees that would certainly be helpful. You have taken back four or five. Certainly there have been discussions over that issue,” Mr Tuttle said.

The matter is probably the last substantive work left for Mr Tuttle, who steps down from his job in a month. The former car salesman from California has had a rocky three and a half years in London, when relations were strained by the war in Iraq, the unpopularity of the Bush Administration and Mr Tuttle's dispute with Ken Livingstone over the refusal of US diplomats to pay the congestion charge.

The former Mayor of London accused the Ambassador of being a “chiselling little crook” for insisting that diplomats were exempt from the charge because it was a tax. Mr Tuttle, 65, said that “being personally, maliciously slandered by a public official” was the lowest moment of his tenure.

Although a Republican appointee, Mr Tuttle did speculate about Britain's ties with the Obama administration. He described the Anglo-American tie as the “most important bilateral relationship in the world” and predicted that it would endure, not least because of the strong military alliance.

As for the role of the US Ambassador to London, Mr Tuttle admitted that much modern diplomacy was conducted directly by leaders and foreign secretaries. His greatest achievement was the public diplomacy conducted to improve America's image in Britain. He said that while George Bush may be unpopular, history would judge his policies in Iraq, and in particular his aid to Africa, more favourably.

At the US Embassy in Grosvenor Square, Mr Tuttle is likely to be remembered as the Ambassador who oversaw the move to new premises being planned south of the Thames at Nine Elms. “It will be fun for me in five or 10 years from now to read about the opening of a new building,” he said. “We will always have Grosvenor Square,” he added, adapting a quote from the film Casablanca.

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