White House Counsel Charles Ruff closed the first day of defence proceedings with a call for senators to step back from the "horrific" option of ousting Mr Clinton from office. His appeal came only hours before Mr Clinton was due to make his annual State of the Union speech.

Charles Ruff: "We are not here to defend William Clinton the man"

Speaking from the floor of the Senate, Mr Ruff began with a calm yet rigorous defence of the president, who stands accused of perjury and obstruction of justice stemming from the Monica Lewinsky affair.

"William Jefferson Clinton is not guilty of the charges," Mr Ruff stated, in front of the 100 gathered senators who will act as the president's jury.

But in his closing remarks, Mr Ruff appealed to members' emotions.

Charles Ruff launches the President's defence

"We are not here to defend William Clinton the man. He - like all of us - will find his judges elsewhere," said Mr Ruff.

"We are here to defend William Clinton, the President of the United States, for whom you are the only judges."

He impressed upon senators the magnitude of their task.

"Are we at that horrific moment in our history when our union can only be preserved by taking this step that the framers saw as a last resort?"

As he spoke, the president will have been busy preparing for his annual speech to both houses of Congress, which sets out his policy plans for the coming year. The televised address will begin at 0200 GMT.

Mr Clinton is expected to focus on key issues such as education, social security, the fight against crime and the "unprecedented economic expansion" in the hope of deflecting attention from the trial.

The White House said he would not mention the trial in his address.

On the fourth day of the historic trial, Mr Ruff made plain that his team would defend the president to the hilt.

Charles Ruff, closing statements: "He must not be removed from office"

He sought to tear apart the prosecution case, which accounted for the first three days of the trial, and called their efforts nothing more than a "rush to judgment".

He said the case against Mr Clinton would not stand up in a "court anywhere" and claimed the 13-strong prosecution team had been "convinced by their own rhetoric".

Bill Clinton: Due to make his address soon after the hearing

In a mostly measured and closely argued submission, Mr Ruff said Mr Clinton was not guilty of the two charges laid against him and should not be removed from office.

He saw "no basis on which the Senate can or should convict the president on any of the charges," said the veteran Washington lawyer from his wheelchair.

He went on to rebuff Republican demands for witnesses to be called to the trial.

But the issue of witnesses remains a thorny one, which threatens to split the two-party Senate.

The relatively bipartisan atmosphere in the upper house is under increasing strain as Republicans press the case for calling trial witnesses, which could include Ms Lewinsky and the president.

Democrats remain fiercely opposed but with only 45 members out of the total 100, they are likely to be outvoted on the issue, which requires only a simple majority to be passed.

Despite the public goodwill towards Mr Clinton and the fact that a two-thirds majority vote will be needed to oust him from the White House, the Democratic defence team must present a convincing case.

Many senators were surprised by the case put by the Republican prosecution team, which was perceived to be highly persuasive. They spent 16 hours over three days detailing their arguments.

Clinton strengthens team

White House spokesman Joe Lockhart said Democrats have bolstered their defence team, in what is thought to be a direct response.

Mr Lockhart said some Democratic members of the House of Representatives Judiciary Committee will join the team.

They will be given 24 hours in total - though are expected to take less time - to set out their defence of Mr Clinton against charges of perjury and obstruction of justice.