The three-day trip, announced by the White House on Thursday and later confirmed by Downing Street, sees Brown hold talks with US President George W Bush at his Camp David retreat.

The White House and Downing Street said there would be a broad agenda, ranging from the situation in Iraq and Iran's disputed nuclear programme to the crisis in Darfur, Europe, Kosovo independence and United Nations reform.

Brown then heads to New York for a meeting with UN Secretary General Ban Ki-moon and to address the assembly.

It was at the US head of state's Maryland bolthole in 2001 that Brown's predecessor Tony Blair first met Bush, amid doubts about how a centre-left Labour prime minister would get on with a right-wing Republican president.

Bush immediately saw common ground, jokingly declaring their shared taste in toothpaste.

After the September 11, 2001 attacks on the United States, Bush and Blair developed a joint commitment to fighting extremism around the world, that controversially took both countries into Iraq and contributed to Blair leaving office early.

With opposition to the US-British presence in Iraq still strong, Bush and Brown's every word and gesture among the log cabins will be scrutinised to detect any cracks in the "special relationship."

The British media have been looking at whether Bush's new partner -- by reputation a fiercely intellectual political obsessive who does not suffer fools gladly -- would be as supine or uncritical as they believed Blair to be.

A new book out later this month argues Britain should now have a more mature debate about relations with the United States, its publishers the centre-left think-tank the Institute for Public Policy Research said Saturday.

The IPPR, which was favoured by Blair, said Bush's doctrine is a "bad mismatch" for tackling security threats nowadays. Instead, Brown's new national security strategy should determine relations.

Bush has described Brown as "open and engaging" and a "long-term thinker." Brown has only said he hopes to forge a strong relationship based on the two countries' shared values.

Some saw Brown's response as equivocal when he was asked in a May 10 interview with Time magazine about his impressions of Bush and whether he was "a man you can do business with."

"President Bush is the elected leader of the American people. I was pleased to have a chance to talk to him," he said, referring to their apparently impromptu meeting at the White House earlier this year.

Much was also made of a speech Brown's International Development Secretary Douglas Alexander gave in Washington on July 13, saying a nation's strength was no longer judged on its military might, but "soft power" and multi-lateralism.

The following day, Mark Malloch Brown -- a junior foreign minister and former UN deputy secretary-general -- suggested London and Washington would no longer be "joined at the hip."