Will they, won't they? Debate clash finally on

After two days of high drama, Republican White House hopeful John McCain has finally agreed to join Democrat Barack Obama for the first of three key debates in the US elections.

上海性息

Forty years to the day after the first televised debate between John F Kennedy and Richard Nixon transfixed the nation, the 2008 showdown was set to go ahead on Friday at the University of Mississippi at 8pm (1100 AEST Saturday).

WATCH LIVE STREAM OF THE DEBATE (FROM 11AM AEST)

IN DEPTH: Visit our US elections minisite

RELATED: McCain blamed for derailing finance talks

RELATED: McCain suspends White House campaign

YOUR SAY: Who do you think will make the best US president?

BLOG: America Decides – Senator Hothead

McCain had kept everyone guessing about his plans for about 48 hours, after dramatically suspending his campaign on Wednesday to rush back to Washington for talks on the financial meltdown.

But his campaign finally confirmed on Friday that enough progress had been made in the talks in Congress on a $US700 billion ($A839.53 billion) Wall Street bailout that the senator would fly to Oxford, Mississippi for the debate.

With Obama ahead in the opinion polls and vowing to go ahead with the Mississippi event with or without his rival, McCain announced that he was “resuming all activities” and heading to the debate.

Campaign resumes

“The McCain campaign is resuming all activities and the senator will travel to the debate this afternoon,” his campaign said in a statement.

“Following the debate, he will return to Washington to ensure that all voices and interests are represented in the final agreement, especially those of taxpayers and homeowners.”

McCain spent fewer than 24 hours in Washington discussing the bailout plan with fellow congressmen and administration officials.

The clash will take place at a rare moment of national peril, with the staggering US financial system spawning a global crisis, the stock market reeling and the life savings of millions of Americans in the balance.

Tens of millions of television viewers are expected to tune into the contest, five weeks before the November 4 election day.

In 2004, more than 62 million people watched the first debate between President George W Bush and John Kerry – given the historic potential of this year's gripping election race, analysts expect an even bigger audience.

Economy teetering

With under 40 days to go before the election, Obama had argued it was more important than ever for the American people to hear from the two men battling to be the next president.

“One of us is going to be in charge of this mess in four months, and the American people I think have a right and obligation to find out where we want to take the country and what we believe,” the Illinois senator, 47, said.

With the economy teetering, US troops mired abroad in two wars and a highly unpopular Republican president, all conditions should benefit Obama.

But the Democrat still has not closed the deal and so he faces intense pressure at the debates to convince voters he is ready to serve as president.

Obama goes into the debates on a surge of momentum, after recapturing the lead in national polls: a Gallup daily tracking poll on Friday gave him a 50 to 44 per cent lead among registered voters.

McCain, 72, has endured a rough week, struggling to frame a consistent message on the crisis and trying to evade Obama's attempts to saddle him with the Bush administration's unpopular economic legacy.

Debates 'crucial' to vote

But analysts said a strong performance by either candidate in the debates, or a string of gaffes, still have the potential to remake the race in the crucial final stretch up to the vote.

“There will be a significant number of people tuning in for the first time,” said University of Arkansas political scientist Andrew Dowdle.

“The images of the candidates still seemed to be unformed, and elastic at this point.”

Presidential debates have often played a crucial role in the outcome of elections.

Kennedy appeared young and dynamic in 1960, outpointing his rival Nixon and emerging victorious in November.

In 1980, Ronald Reagan used the debates to pass the test of presidential credibility and went on to beat president Jimmy Carter.

Four years later, he put to rest questions about his advanced age – swatting challenger Walter Mondale with the immortal line: “I am not going to exploit for political purposes, my opponent's youth and inexperience.”