WASHINGTON - Republican presidential candidate Herman Cain dodged reporters' questions Wednesday as he tried unsuccessfully to divert attention from a fast-moving and potentially campaign-derailing sexual harassment scandal.

Cain, a surprise leader in the race to find a challenger to Democratic President Barack Obama, got testy with reporters and continued to denied any wrongdoing after reports surfaced that he faced sexual harassment accusation from two women when he was the head of the National Restaurant Association.

Then on Wednesday afternoon, a third former employee told The Associated Press that she had considered filing a workplace complaint over what she considered aggressive and unwanted behaviour by Cain when she worked for him in the 1990s. She says the behaviour included a private invitation to his corporate apartment.

The employee described situations in which she said Cain told her he had confided to colleagues how attractive she was and invited her to his corporate apartment outside work. She spoke on condition of anonymity, saying she feared retaliation.

The two women whose cases were first reported are barred from publicly giving their accounts by confidentiality agreements they signed in exchange for financial settlements from the trade group. On Wednesday, Cain was under pressure to ask the group to release the women from those agreements.

Confronted by reporters after he left a speech to health care professionals in Virginia, Cain told them "don't even bother" asking about the scandal.

When pressed about the allegations, Cain raised his voice and said "What did I say? Excuse me. Excuse me!" as hotel security led him through a hotel hallway jammed with journalists.

His campaign manager Mark Block said he would address the questions "when it's appropriate."

Cain, a former restaurant lobbyist and pizza chain CEO, later travelled to Washington as part of a previously scheduled tour to introduce himself to the nation's power brokers.

He has stunned the political establishment with his rise to the top of polls, often topping the presumed front-runner, former Massachusetts governor and venture capitalist Mitt Romney. Cain appeals to some conservatives because he is a political outsider at a time of anti-Washington sentiment that could help the Republicans challenge Obama in 2012.

But the night before his first appearances the news website Politico said that two women reportedly received financial payments from the National Restaurant Association after complaining of inappropriate sexual behaviour in the 1990s by Cain, who was then in charge of the lobbying group.

The candidate at first denied knowing anything about the allegations. But in a string of media appearances that followed, he began recollecting more details, leading many to suggest that he was changing his story. Media attention then surged.

Try as he might to project an image of campaign business as usual, he couldn't escape the questions that have dogged him since the allegations surfaced three days ago.

So far Cain's supporters are rallying behind the candidate. But the scandal could threaten his standing near the front of the Republican field, which will quickly begin thinning out after the first contest in Iowa in January, if more embarrassing details emerge.

Joel P. Bennett, the lawyer for one of two women, said in media interviews Tuesday that he had asked the trade group to waive an agreement and allow her to talk openly about her allegations and to respond to Cain's claims that the complaints were "totally baseless and totally false."

"I know her very well," he told CNN late Tuesday, "and I'm sure she would not make a false complaint."

Bennett told The Associated Press he would have more to say after he meets with his client Wednesday.

A source contradicted that on Wednesday, telling AP that despite her lawyer's claims, the woman who accused Cain of harassment is reluctant to talk about the episode in public. The person, who spoke on the condition of anonymity because of the sensitivity of the accusations, said no decision has been made about asking the National Restaurant Association to release the woman from a confidentiality agreement that was part of her settlement and that the fact that the incident has become public is very unsettling to the woman.

A spokeswoman for the restaurant association, Sue Hensley, said Tuesday night that the group had not been contacted by Bennett.

The New York Times reported Tuesday night that the trade group gave a female employee a year's salary in severance pay, $35,000, after she said an encounter with Cain made her uncomfortable working there. The newspaper cited three people with knowledge of the payment to the woman, who was not Bennett's client.