By backing down over the legal issue of "executive privilege" the White House has avoided a high profile showdown with the Supreme Court that had dangerous echoes of Watergate and the downfall of President Nixon.

Executive privilege is a defence used by presidents to stop investigators finding out too much of what has happened in the White House.

It is based on the premise that private discussions between the president and his White House staff are subject to the same kind of legal protection as discussions between an attorney and their client.

Battle with the chief prosecutor

Kenneth Starr's attempts to make two key White House aides, Bruce Lindsey and Sidney Blumenthal, testify against the president is just the latest chapter in the case he is attempting to build against Mr Clinton.

• Starr's case began as an investigation into the Whitewater land deals made by Clinton when he was Governor of Arkansas.

• Earlier this year the investigation was extended to see whether Clinton had lied under oath about having an affair with Monica Lewinsky, a former White House intern, and obstructed justice by asking her to cover up the affair.

• Starr believes that the White House aides may have vital information that could help bring President Clinton down

Bid to revive waning Starr?

Ken Starr: Still on the trail of the president

The chief prosecutor is trying to put together a case that could lead to President Clinton's impeachment by Congress and removal from office, justifying his long and expensive inquiry.

In response, the White House invoked executive privilege to stop staff testifying, but in May a federal judge argued that the aides should testify leading to a White House appeal.

But when Kenneth Starr petitioned the court for a quick judgement, the White House withdrew its case, aiming to prevent a quick resolution and judgement by the court.

Dangers of history

What is so dangerous about the use of executive privilege - and a key reason why Clinton avoided going all the way to the Supreme Court to defend it - are the overtones of the Watergate scandal and downfall of President Nixon.

Nixon: Faced threat of impeachment

The notion of Executive Privilege was defined in a 1974 Supreme Court ruling, United States v. Nixon which said that private conversations were protected but the Court also rejected President Nixon's claim of an absolute privilege (such as attorney-client) that completely shielded disclosure of all internal communications.

The Court argued that unless there was the need to protect military, diplomatic or national security secrets, the president's general interest in confidentiality could be outweighed by the clear and demonstrated need for evidence in a criminal proceeding.

Defeat in the showdown meant that Nixon had to turn over the tapes of conversations in the Oval Office and only 17 days after the unanimous ruling he resigned.

Tactical retreat

Clinton's change of tack was no doubt partly guided by the desire not to be the first president since Nixon to take an executive privilege claim to the Supreme Court, a case he would probably have lost.

But the retreat is only important if it leads to White House aides to incriminate the president. Indeed the White House has indicated it will use other legal manoeuvres, such as claiming attorney-client privilege for Lindsey, to stop them testifying.

Even if they did testify there are indications that they would not incriminate Clinton.