Tony Blair has begun his final official visit to the US as prime minister, during which he will hold talks with President Bush.
Mr Blair has said he will stand down on 27 June
Mr Blair has said he still has much work to do on domestic and global issues before standing down on 27 June.
He and Mr Bush are expected to discuss Iraq, the Middle East and climate change ahead of next month's G8 summit.
Mr Blair arrived at Andrews Air Force base, near Washington, on Wednesday and later had dinner at the White House.
He is staying at the White House ahead of a working session in the Oval Office and a joint news conference with Mr Bush on Thursday.
During an American television interview, the prime minister praised George Bush as a strong leader who had been true to his word.
He also called on Americans not to go down the road of isolationism.
"The biggest danger is if America disengages, if it decides to pull up the drawbridge and say to the rest of the world 'Well you go and sort it out.'
"We need America engaged," he told US television network NBC.
There will also be a reception at the British Embassy, to mark the restoration of devolved government in Northern Ireland.
The prime minister's official spokesman said: "The World Trade Organization talks will be high on the agenda because we are approaching crunch point. The run-up to the G8 will be important, particularly on climate change."
The G8 summit takes place in Germany in June, and Mr Blair is keen to pursue green issues and aid for Africa, as well as sending a "very clear message" on Darfur telling the Sudanese government to come into line with international, UN-backed demands.
But Lib Dem leader Sir Menzies Campbell said: "While Tony Blair and George Bush say their last goodbyes and exchange warm tributes, the British public are right to think that their relationship has resulted in untold damage to our reputation at home and abroad."
He said Gordon Brown - in line to be the next prime minister - should end what he called the "slavish relationship" with the US and instead be a "candid friend".
Mr Brown should call for the closure of Guantanamo Bay, set a target for withdrawing British troops, renegotiate reciprocal extradition laws and urge President Bush to sign up to the Kyoto treaty, he said.