Washington: Republican presidential hopeful Herman Cain will decide before December 5 on whether to quit the race for the White House as claims of a 13-year affair threatened to end a campaign dogged by sex scandals.

Cain, once the front-runner to take on President Barack Obama in November 2012 elections, has denied wrongdoing, saying he was only friends with his latest accuser, Ginger White, who says they had a sexual relationship.

"Before Monday we'll make a decision," Cain said in an interview on Fox News yesterday, admitting that a flurry of allegations of misconduct had sent his presidential bid "off message."

"It's not fair to my family, it's not fair to my supporters, it's not fair to this campaign, it's every week, now three out of four weeks we've been hit with another one of these accusations," he said.

"The decision could be we're going to continue with this campaign, full speed ahead. The decision could be we're going to suspend the campaign.

"If my wife says, you know, terminate the campaign, would I quit? The answer is, yes, but she wouldn't do that. That's not the kind of wife I have. My wife has been supportive of me, she is with me," Cain added.

Cain, a former pizza company executive, has already faced allegations that he sexually harassed several other women, all of which he has denied and seen his ratings drop in the opinion polls.

He announced in a staff conference call on Tuesday that he was reassessing the viability of his bid for the Republican Party nomination to take on Obama.

Cain, 65, rose dramatically in the polls in September and October, but his approval ratings have since dipped amid a series of lurid accusations.

In the latest blow to his campaign, White, from Atlanta, alleged her affair with Cain, who is married, ended just eight months ago.