Ahead of his first meeting as prime minister with George W Bush, Brown gave no relief to critics in his centre-left Labour Party unhappy at the close ties his predecessor Tony Blair forged with the right-wing Republican president.

"It is in the British national interest that the relationship with the United States is our single most important bilateral relationship," Brown said in a statement.

"It is a relationship that is founded on our common values of liberty, opportunity and the dignity of the individual.

"And because of the values we share, the relationship with the United States is not only strong but can become stronger in the years ahead."

Brown and Bush hold talks at the US president's Camp David retreat Sunday and Monday, with US-British involvement in Iraq, the nuclear stand-off with Iran, the Middle East peace process and Darfur all up for discussion.

The prime minister then flies from the US head of state's Maryland bolthole to meet United Nations Secretary General Ban Ki-moon in New York and address the UN assembly on Tuesday, a Downing Street spokeswoman said.