Prime Minister Gordon Brown will meet all three major U.S. presidential candidates on Thursday before seeing President George W. Bush, a reminder that world leaders are now looking beyond Bush to his successor.

Brown, on his second U.S. visit since taking office last year, holds talks in rapid succession with presumptive Republican nominee John McCain and the Democrats vying for their party's nomination, Hillary Clinton and Barack Obama.

He then goes to the White House to meet Bush, who shares the British prime minister's plight - low popularity and economic problems at home.

With Bush in the twilight of his presidency, Brown is expected to walk a fine line, keeping some distance on issues like the unpopular war in Iraq while preserving Britain's long-standing "special relationship" with the United States.

Brown said on Wednesday he would seek "coordinated action" to shore up the global economy, plagued by a credit crunch, record oil prices and market turmoil.

Determined to avoid being tagged as "Bush's poodle" like his predecessor Tony Blair, Brown seems as eager to lay the groundwork for closer relations with the next president as he is to maintain ties with the current one.

A round of 45-minute sessions at the British ambassador's residence could yield clues to how the winner of the November election might change policies that have at times rankled Britain and other European allies.

Brown has made clear his own hopes for an improved partnership between Europe and Washington under the next U.S. administration. "It's partly because the divisions within Europe over Iraq will come to an end," Brown told ABC's "Good Morning America" program.

NO ENDORSEMENT

While Brown is closer on the political spectrum to the two Democrats than to McCain, Bush's fellow Republican, all three have taken stands that could win favour with the head of the Labour Party.

They have signalled, for example, they would all do more to fight global warming and revamp the Bush administration's internationally criticized treatment of terrorism suspects.

McCain's sharpest difference with Democratic rivals is on Iraq. He backs Bush's strategy of maintaining a heavy U.S. troop presence. Clinton and Obama want a withdrawal timetable.

For his part, Brown has stirred unease in Washington over Britain's phased drawdown in Iraq, where Blair had bucked British public opinion in joining the 2003 U.S.-led invasion.

Brown told ABC he had no plans to endorse any U.S. candidate, seeing that as a decision for American voters.

But even as his three-day U.S. tour has been eclipsed in the U.S. media by Pope Benedict's visit this week, the 57-year-old Scot has seemed eager to reach out to Americans. "I love America, and I love watching American TV," he said.

That, however, may not help his poll ratings at home, which have been dropping faster than any British leader since before World War Two.

Brown, like Bush, has seen his economic stewardship come under fire, raising speculation that he could soon face a challenger for his party's leadership.

With less than 10 months left in office, Bush is struggling to stay relevant but is having a harder time swaying world leaders looking to whomever will succeed him in January 2009.

Brown has already struck a notably cooler relationship with Bush than Blair. Their last U.S. meeting at Camp David in July was marked by stiff formality.

This time, Brown will be accompanied by his wife, and Bush will try to break the ice with a social dinner in the White House residence.