But after the first day of the historic impeachment trial, New York Democrat Charles Schumer said the proceedings had uncovered no new revelations.

He said: "It was the same thing I've heard in the House for the last three months. I think some in the House hope that if they keep saying it enough maybe public opinion will change. I don't think so."

Democrat Charles Schumer: "Nothing new"

Republicans argue that without witnesses being allowed to give testimony, which Democrats fiercely oppose, there will be no opportunity for new evidence.

But he also said the next few days, when the question of witnesses again becomes an issue, could see the Senate's reputation for being bipartisan ripped apart.

'Above the law'

Mr Clinton is charged with committing perjury and obstructing justice over his affair with former White House aide Monica Lewinsky.

Laying out their arguments in the first Senate impeachment trial since 1868, the House prosecutors said that allowing the president to break the public trust "poses a far greater threat to the liberties guaranteed to the American people by the Constitution than anything imaginable".

Republican James Sensenbrenner told the Senate failure to bring Mr Clinton to account would cause a cancer in society for generations to come.

"We are here today because President William Jefferson Clinton decided to put himself above the law - not once, not twice but repeatedly," said Mr Sensenbrenner.

"For these actions he must be held accountable to the only constitutional means the country has available: the difficult and painful process of impeachment."

The trial began with a bang of the gavel by Chief Justice of the Supreme Court, William Rehnquist at 1800 GMT on Thursday.

Rep Henry Hyde: "You are now the stewards of the oath"

After a prayer by the Chaplain and a warning from the Sergeant of Arms that the chamber remain silent on "pain of imprisonment", the Chairman of the House Judiciary Committee, Rep Henry Hyde, began proceedings.

What you do over the next few weeks will forever affect the meaning of those two words 'I do,'" he told the 100 senators.

Rep Henry Hyde: "Listen to the evidence as those who must sit in judgment"

"Depending on what you decide, it will either be strengthened in its power to achieve justice, or it will go the way of so much of our moral infrastructure - and become a mere convention, full of sound and fury, signifying nothing," Mr Hyde said

The 13 House managers, or prosecutors, have 24 hours to present opening arguments against the president. White House lawyers are expected to begin their opening statements on Tuesday, 19 January.

The big picture

On the first day House managers went to great lengths to show a web of deceit.

The BBC's Stephen Sackur: No new bombshells, just a mountain of detail

While prosecutors acknowledge Mr Clinton's actions do not seem to meet the standard of "high crimes and misdemeanours" when looked at individually, they argue they are both "sinister and criminal" when taken as a whole.

The third speaker, Tennessee Rep Ed Bryant said such actions degraded the sanctity of the oath that President Clinton had sworn when he took office.

Rep James Sensenbrenner "Perjury is the twin brother of bribery"

"William Jefferson Clinton, placed his left hand on a Bible in front of his wife, the Chief Justice and every American watching that day and affirmatively acknowledged his oath of office," Rep Bryant said after showing a video of Mr Clinton's inauguration."

A White House spokesman said on Thursday that the prosecution had an "unsubstantiated and circumstantial" case.

"The reality is there is no case for the removal of the president," James Kennedy, special adviser to the White House counsel, said in a statement issued outside the Capitol.

Proving the case

The House prosecutors aim to prove two counts of impeachment - perjury and obstruction of justice - passed by the House of Representatives in December.

Rep Asa Hutchinson described a flurry of activity before Ms Lewinsky's testimony

Arkansas Rep Asa Hutchinson took to the task of presenting the House case of obstruction of justice.

Using slick charts detailing meetings and phone calls between President Clinton, Monica Lewinsky and Mr Clinton's adviser, Vernon Jordan, Rep Hutchinson demonstrated the flurry of activity in the period when Ms Lewinsky gave a signed affidavit in the Paula Jones sexual harassment case.

The phone calls "became a frenzied and concerted effort to keep the holes plugged in the dyke," Rep Hutchinson said.

Later California Rep James Rogan detailed the House perjury case.

He began by showing another video - this time of President Clinton's grand jury testimony on 17 August. In the video, Mr Clinton raises his right hand and swears to tell "the truth, the whole truth and nothing but the truth."