Barack Obama profited from the coveted backing of former secretary of state Colin Powell and a jaw-dropping cash haul entering into the final fortnight of the epic White House race.

The Republican Powell, the first African-American to serve at the apex of the US military as chairperson of the Joint Chiefs of Staff, said the 47-year-old Democrat would be a "transformational president".

Powell carries the burden of his role in promoting the Iraq invasion. But his endorsement was still a stinging rebuff to Republican candidate John McCain (72) and could help sway swing voters and military veterans.

His backing came as the Obama campaign announced a fundraising take of more than $150-million last month, demolishing its previous record of $66-million set in August.

The gigantic treasure trove is enabling Obama, who enjoyed a 10-point lead in Sunday's Gallup tracking poll, to hit McCain even harder with a nationwide advertising blitz in the days leading up to the 4 November election.

'Beyond honoured'

Addressing a carnival-like rally of more than 10 000 supporters, Obama said he was "beyond honoured and deeply humbled to have the support of General Colin Powell."

The Illinois senator said the Fayetteville area of North Carolina, home to the giant Fort Bragg army base, knew something about military heroism.

"And this morning, a great soldier, a great statesman, a great American has endorsed our campaign to change America," he said.

"And he knows, as we do, that this is a moment where we all need to come together as one nation — young and old, rich and poor, black, white, Hispanic, native American, Republican and Democrat."

Powell, on NBC programme 'Meet the Press', said Obama had "met the standard" to be commander-in-chief "because of his ability to inspire" all ages, ethnic groups and political persuasions.

McCain remained a friend, Powell said, before launching a hard-hitting critique of the Republican's rightward lurch, his haphazard response to the US economic crisis and his choice of Sarah Palin as vice presidential nominee.

Powell said that Obama, in contrast, had emerged looking presidential with a "steadiness, an intellectual curiosity, a depth of knowledge" in his approach to the financial tumult.

Make all Americans 'proud'

The nation's first black secretary of state added that victory by the mixed-race Obama in two weeks would make all Americans "proud," not just African-Americans, and would "electrify the world".

Speaking on Fox News on Sunday, McCain said he had "always admired and respected General Powell."

"We're long-time friends. This doesn't come as a surprise," the Arizona senator said, touting his endorsement by other former secretaries of state including Henry Kissinger, James Baker and Lawrence Eagleburger.

McCain also defended automated "robo-calls" unleashed by his campaign in at least 10 swing states, insisting the charges that Obama is a closet radical who would subvert democracy were "legitimate and truthful".

The tenor of McCain's campaign, whose robo-calls also accuse Obama of supporting the killing of babies born alive in abortions, was bitterly decried by Powell along with anti-Muslim discrimination in Republican circles.

McCain renewed his condemnation of Obama's economic policies as "socialism" and warned a rally in Toledo, Ohio that Obama planned to "redistribute wealth" to the "more than 40 percent of Americans" who are too poor to pay income taxes.

"Barack Obama's plan is to raise taxes on some in order to give checks to others. It's not a tax cut, it's just another government give away," McCain told the crowd.

McCain said he wants to spread opportunity by cutting taxes on the businesses which create jobs, whereas "Senator Obama is more interested in controlling who gets your piece of the pie than he is in growing the pie."

Obama said McCain backed tax cuts for wealthy corporate bosses "who've been making out like bandits."

Stopping by Fayetteville's "Cape Fear" barbecue restaurant, Obama was accosted by 54-year-old shop worker Diane Fanning, who yelled "socialist, socialist, socialist — get out of here!"

Fanning refused to shake Obama's hand when he offered it, and she told reporters that Powell was a "Rino" — Republican In Name Only.

Other customers were more welcoming of Obama as he foraged for votes in North Carolina, which last backed a Democratic presidential hopeful in 1976 but which like other Republican "red" states is now very much in play.

Furniture salesman Mike Long (33) said he had been less than 50 percent likely to vote for Obama. But after discussing health care with the candidate, he was now "98 percent" certain to do so.

AFP