Mr Harry Thomason, a close friend of President Clinton, emerged from a grand jury hearing yesterday saying, "I've always believed the President was telling the truth", writes Joe Carroll.
Mr Thomason was summoned to the White House when the Monica Lewinsky story broke in January and spent hours discussing the situation with the President and Mrs Hillary Clinton.
Speculation that Mr Clinton was considering changing his mind about testifying to the grand jury on Monday because of international problems was dismissed by a White House spokesman. Mr Joe Lockhart said he was not aware of any plans to delay or limit Mr Clinton's appearance.
The President is travelling outside of Washington on a fundraising trip. However, he will return earlier than planned to the capital to be at Andrews Air Force Base when the bodies of US personnel killed in the embassy bombings in Africa arrive tomorrow.
Mr Thomason, a Hollywood producer, stayed several weeks in the White House early this year. He testified yesterday for 90 minutes before the grand jury.
Mr Thomason had advised Mr Clinton to make a more forceful denial of having had sexual relations with Ms Lewinsky in January. The President's first denials on TV were seen an hesitant.
Mr Thomason is expected to stay in Washington to help the President with his appearance before the grand jury on Monday. The testimony will be given in the White House over a live TV feed to the jury in a Washington courthouse.
Mr David Kendall, the President's personal lawyer, yesterday was allowed to view a videotape of Mr Clinton's testimony on January 17th in which he denied that he had sexual relations with Ms Lewinsky. This was when he was questioned by lawyers for Ms Paula Jones, who was suing him for sexual harassment.
Lawyers say that it will be important for Mr Kendall to have seen this videotape as he coaches the President for next week's appearance. This is expected to put him at odds with Ms Lewinsky who has now retracted her denial under oath of having sex with Mr Clinton in the White House.
Some of the President's political advisers are reported to be urging him to reconsider his decision to testify. It is argued that the bombings of US embassies in Kenya and Tanzania last week and the new crisis over UN weapons inspections in Iraq could be grounds for the President asking to postpone his testimony which he has agreed to give voluntarily.
If the President did decide not to testify, independent counsel Mr Kenneth Starr would have to seek a new subpoena to compel his appearance. However, some lawyers say that the President could refuse the subpoena and ask the Supreme Court to rule on its constitutionality.
Mrs Clinton said yesterday that it was prejudice against the President's home state of Arkansas which was driving much of the investigation against him. She told the Arkansas Democrat in a telephone interview that at the White House "it's just more of the same".
"I think a lot of this is prejudice against our state. They wouldn't do this if we were from some other state," she told the newspaper.