Britain's prime minister told President Bush he backed the invasion of Iraq while he was still seeking a second U.N. resolution on the military action, British media reported Thursday.

Tony Blair is alleged to have told Bush in January 2003 he was "solidly behind" U.S. plans for military action, despite the continuing negotiations, according to reports in the Guardian newspaper and on a British television station. They both quote a new version of a book due to be published Friday.

The book, "Lawless World," is by lawyer Philipe Sands, who practices at the same law firm as Blair's wife.

The newspaper, which published the report on its Web site, and Channel 4 News claim to have seen a memo recording a meeting between Blair and Bush at the White House on Jan. 31, 2003.

During the talks, it is claimed Bush told Blair the "diplomatic strategy had to be arranged around the military planning."

The reports claim Blair said he was "solidly with the president and ready to do whatever it took to disarm Saddam."

A spokesman at Blair's office, speaking on the customary condition of anonymity, said Thursday he could not confirm the contents of the memo and said officials "don't comment on the prime minister's conversations with other leaders."

"The prime minister only committed forces to Iraq after securing the approval of the house in the vote of March 18 2003," the spokesman said.

He said the decision was taken "only after other routes to disarm Iraq had failed" and that "during this time there were frequent discussions" between Britain and the United States about Iraq.

The book claims that the memo undermines Blair's speech to British lawmakers in February 2003, when he said he was giving Saddam Hussein a final chance to disarm voluntarily.

The news organizations claim the memo records Bush as saying the United States would "put its full weight" behind efforts to secure a second U.N. resolution, but that "military action would follow anyway."

Blair sought to win U.N. support with the second resolution, which would have given Hussein an ultimatum to disarm — and carried the threat of military action.

It is claimed Bush told him the resolution "would provide an insurance policy against the unexpected, and international cover, including with the Arabs".

The lawyer's book also claims Bush told Blair the United States had considered a possibility of "flying U2 reconnaissance aircraft with fighter cover over Iraq, painted in U.N. colors."

Bush allegedly claimed that if Iraqi forces fired at the aircraft, the country would be in breach of existing U.N. resolutions.

He is also alleged to have expressed hopes that a defector could be found who could "give a public presentation about Saddam's" weapons of mass destruction. The memo claims Bush also told Blair there was a possibility Saddam would be assassinated.

In the book, Sands claims the memo records Bush as saying it was "unlikely that there would be internecine warfare between the different religious and ethnic groups" in the aftermath of an invasion.

"If these allegations are accurate, the prime minister and President Bush were determined to go to war with or without a second U.N. resolution, and Britain was signed up to do so by the end of January 2003," Sir Menzies Campbell, acting leader of the opposition Liberal Democrat party, said in a statement.

"By then it was clear that there was no credible evidence of weapons of mass destruction — the stated justification for the moves against Saddam Hussein."

He said diplomatic efforts after January 2003 appear now to simply have been a case of going through the motions.

"The prime minister has a lot of explaining to do," Campbell said.