Ms Monica Lewinsky finished a day of testimony to the grand jury with CNN reporting that she claimed to have had sex about a dozen times with President Clinton. But she denied that he tried to get her to lie under oath.
The CNN White House correspondent, Mr Wolf Blitzer, citing "two sources familiar with the testimony", reported that the former White House intern testified that the affair continued over 18 months from the autumn of 1995.
President Clinton testified last January that he never had sexual relations with her or asked her to lie - and could not recall being alone with her.
A spokeswoman for Ms Lewinsky said she had "answered each question truthfully, completely and honestly". The Independent Counsel, Mr Kenneth Starr, has the option of recalling her before the grand jury next week or after President Clinton testifies on August 17th.
Ms Lewinsky, who recently celebrated her 25th birthday, looked tense when she arrived at the courthouse.
Over at the White House all eyes were on President Clinton as he attended a function in the Rose Garden to support stricter gun control laws. As reporters shouted questions at him about Ms Lewinsky, the White House Marine band struck up a march and drowned them out. He probably would not have answered them.
Mr Jim Kennedy of the White House Counsel's office hoped Ms Lewinsky's testimony would "bring a close to this four-year enquiry". This was a reference to the full Whitewater investigation by Mr Starr, at a cost of $40 million.
A friend of Ms Lewinsky told media that in preparations with her lawyers she broke down and cried at one stage. She was said to be upset that her testimony could hurt the President. One source described her as "an emotional wreck".
Meanwhile, a man who appears in a video film showing new pictures of Mr Clinton embracing Ms Lewinsky at a Democratic function in Washington two years ago has said the organisers asked him to watch over her as she "might do something silly".
Mr John Sullivan, an Indianapolis attorney, said he was told that Ms Lewinsky was "showing up at events and fantasising about the President". The organiser, Ms Regan Burke, a government employee, had said: "We want to make sure she doesn't kiss him or do something to embarrass the President," Mr Sullivan said.