U.S. Republican presidential hopeful Herman Cain has told aides he is reassessing the viability of his campaign after a woman from Georgia alleged she had a 13-year affair with him.

The accusation of infidelity follows a series of sexual harassment allegations that have already complicated Cain's pursuit of his party's nomination.

In a Tuesday morning conference call with his staff, transcribed by the conservative National Review magazine, Cain denied the affair, calling it just a friendship and saying he was trying to help the woman financially. But he said the allegation is still “cause for reassessment.” The magazine quoted Cain as saying he has to determine whether it will “create too much of a cloud ” in people's minds for them to continue supporting him.

The former pizza executive said people will have to decide whether they believe him or the accuser. Cain said his team is going to give it time to gauge the response and said he would continue his campaign schedule as usual during the next several days.

Once seen as a top rival to former Massachusetts governor Mitt Romney, Cain suffered a drop in support when he was forced to respond to allegations of sexual harassment dating back to the late 1990s.

Cain also had some awkward moments on foreign policy, including a fumbled answer when asked to comment on President Barack Obama's policy on Libya.

Cain's struggles have cleared the way for former House of Representatives speaker Newt Gingrich to surge ahead in public opinion polls.