In an editorial, the Times said the United States may hesitate to use Blair to try to broaden support for its policies and urged the British leader to distance himself from "American-style spin operations" and be tougher with President George W. Bush.

Blair's domestic popularity has taken a heavy blow from his support for the US-led war in Iraq and claims that his government exaggerated intelligence findings on how quickly Iraq could fire chemical and biological weapons.

"The White House therefore has every reason to be concerned about the British prime minister's growing credibility problems at home," said the editorial.

"Mr Blair's grip on office doesn't seem threatened. But his once legendary ability to sway public opinion has taken a large and largely self-inflicted hit.

"The next time Washington needs to borrow some of his credibility to broaden domestic support for its international policies he may have little to spare.

"We credit the sincerity of Mr Blair's beliefs, but are troubled by the unworthy, and ultimately counter-productive, ways he used to advance them."

The key US newspaper said Blair's standing could rebound if events in Iraq prove he was right and an official inquiry shows his administration had no role in the suicide of David Kelly, the top Defence Ministry expert on Iraqi weapons programmes.

"He can make that more likely by distancing himself from American-style spin operations. He could also more openly challenge Washington on a number of important issues on which his views are known to diverge from Mr Bush's.

"These include the need for a wider United Nations role in Iraq, the urgency of international action on global warming and the moral imperative of curbing the American and European farm subsidies that condemn developing countries to poverty," concluded the New York Times.

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