Facing hostile questioning in parliament, Prime Minister Tony Blair (search) acknowledged on Tuesday some friction in his close relationship with President Bush and the political problems the friendship causes at home.

Blair used his sharpest language yet in the long-standing disagreement over the Bush administration's detentions at the U.S. Navy base in Guantanamo Bay, Cuba (search), saying they "must end." And the British leader said it was likely weapons of mass destruction may never be found in Iraq.

"I have to accept that we have not found them, that we may not find them," Blair told the House of Commons Liaison Committee. "We do not know what has happened to them. They could have been removed, they could have been hidden, they could have been destroyed."

Blair rejected any suggestion that the stockpiles never existed and that Saddam had not been a danger to the world.

"To go to the opposite extreme and say therefore no threat existed from Saddam Hussein would be a mistake," he said.

During a two-and-a-half hour session before a House of Commons committee, Blair was grilled about his relationship with Bush, and he defended the alliance in the war against terror, insisting it was in Britain's best interest.

"I am not daft about the politics of it. I can see, particularly in my own political family, it is a problem from time to time," said Blair, who has faced intense criticism within his Labour Party over the Iraq war.

"I don't think this country should ever let itself be ashamed of its relationship with the United States of America or believe that Britain is America's poodle."

Blair acknowledged two key differences with Bush: Washington's refusal to sign the Kyoto protocol on climate change; and the detention of four Britons at Guantanamo Bay.

"Guantanamo Bay is an anomaly that at some point has got to be brought to an end," Blair said.

But, he said, the United States is not unreasonable in detaining people it considers a security threat. And he said dialogue would continue on global warming.

Blair also suggested the U.S. position was softening on the Kyoto protocol, and that Washington now accepted the scientific arguments.

"I do not think we should give up on the dialogue with the United States," the prime minister said. "I think they accept the science. The question is what do you do about it? That is in itself a significant change that we need to build upon."

Blair has said global warming will be a key issue when Britain chairs the Group of Eight summit next year. The 1997 Kyoto Protocol, reached at an international meeting in Japan, sets the target of bringing emissions of carbon dioxide and other greenhouse gases worldwide eight percent below the 1990 level by 2010.

The line of questioning, from all parties, betrayed the deep unease among many Britons who feel their government slavishly follows U.S. foreign policy without exerting real influence.

"Surely we, the country, have a right to know, where we have gone to war, where you have put yourself shoulder to shoulder with the Americans ... what we are getting in return?" asked Conservative lawmaker Edward Leigh.

It's widely assumed in Britain that Blair backed Bush over Iraq in return for a pledge that Washington would push harder for peace in the Middle East. A road map peace plan for Israel and the Palestinians put forward by Bush last year has largely stalled.

"Hasn't he let you down? Has he delivered his side of the bargain to you, given all the political capital you have expended in his behalf?" asked Leigh, referring to Blair's slump in opinion polls since the war.

At times exasperated, Blair denied it was a "quid pro quo" relationship in which "every so often they throw us a scrap."

Opinion polls show a majority of Britons dislike the U.S. president and disapprove of Blair's close relationship with him.

Fearing Britain is mired in a conflict in Iraq over which it has no control, several lawmakers have called on Blair to distance himself from Washington, or at least demonstrate influence he bring to the relationship.

Blair suggested on Tuesday he had encouraged Bush to engage the United Nations instead of acting unilaterally after the Sept. 11, 2001 attacks.

He also said Britain had "played a constructive part" in the decision to transfer full sovereignty to an interim Iraqi government and build up Iraqi security forces instead of the "option of a dramatic increase in foreign troops."