Republican prosecutors will argue strongly for Ms Monica Lewinsky and others to appear as witnesses in the impeachment trial of President Clinton, which gets under way in the Senate next Thursday.
But under rules decided last week, the decision on calling her and other witnesses will be delayed.
The White House has strongly opposed the calling of witnesses and has promised to mount a "vigorous, successful and complete defence" of the President.
Beginning at noon on Thursday there will be up to six days of hearings in which the Republican prosecution team and the White House lawyers will set out their respective cases on the charges that Mr Clinton committed perjury and obstructed justice.
The 100 senators, who act as jurors, must sit silently through these presentations.
Next, the senators will be allowed two days in which to question the rival legal teams.
But the questions will have to be submitted in writing through the Chief Justice of the Supreme Court, Judge William Rehnquist, who presides over the trial.
When this phase ends around January 25th, the White House will be allowed to move a motion to dismiss the case on the grounds that the crimes have not been proven and do not merit Mr Clinton's removal even if they were.
A simple majority of the 100 senators would suffice to dismiss the case but even if all the 45 Democrats voted to dismiss, they would need the support of six Republicans to clear Mr Clinton.
If the dismissal motion fails, the Senate would vote on whether to call a list of witnesses.
These would then have to give sworn statements and the Senate would have to vote again whether to call individual witnesses based on their affidavits.
When any witnesses have been heard, the lawyers from both sides will sum up their case, the senators will deliberate in private and then vote on whether to convict Mr Clinton.
A two-thirds majority would be required for conviction.
This complicated procedure was approved unanimously by the Senate last Friday in a spirit of bipartisanship which contrasts with the bitter exchanges between Republicans and Democrats when the House of Representatives voted for the impeachment articles last month.
The Senate majority leader, Senator Trent Lott, promised in a weekend radio broadcast that the trial would be conducted "with civility, order and fairness".
Mr Lott said: "If you follow our proceedings over the next few weeks, whether reading the news or watching us live on television, I think you will see us, together, teach the world that we Americans are very serious when we say `equal justice under the law'. "
Mr Clinton has until noon today to reply formally to the Senate's summons last Friday to answer the impeachment charges. Up to Thursday morning his lawyers and the Republican prosecutors can also file various trial motions except concerning witnesses.
A weekend poll by Time/CNN shows 62 per cent do not believe the Senate should remove Mr Clinton.
Some 63 per cent say Mr Clinton should not resign from office and 69 per cent want him to deliver his State of the Union address to a joint session of Congress on January 19th.
Several members of Congress, from both Republican and Democratic parties, have urged the President to delay his address until the Senate trial is over.
AFP reports from Washington:
DNA tests have proved that Mr Clinton did not father the son of a former prostitute, Time magazine reported yesterday.
The weekly publication reported that tests showed blood samples taken from Ms Bobbie Ann Williams and her son Danny (13) did not match the President's DNA.
"There was no match. Not even close," Time reported, citing a source at the tabloid Star newspaper, which authorised the tests.
The report ends years of speculation over the affair - accounts of which first surfaced in US tabloid newspapers in 1992.
The Star paid the African-American former prostitute for her story and the blood samples after she sold a story to the press alleging Mr Clinton's paternity.