Nixon buffs today have the chance to trawl through more secretly taped conversations and telephone calls by the disgraced president. The latest batch - some of it barely audible - cover January and February 1973.

The period, at the start of Nixon's second term, covers the conviction of burglars whose break-in at the Democratic headquarters precipitated the cover-up that eventually brought down Richard Milhous Nixon.

The new material, released by the Nixon presidential library, include a conversation between Nixon and Charles Colson, his special counsel who was never charged in connection to Watergate.

The two men discuss the state of mind of Howard Hunt, who was jailed for his role in the burglary, the death of his wife in a plane crash and the course of the Watergate trial.

The latest release also includes new discussions involving the president and his aides about using executive privilege as a defence against future investigations. The tapes should be of interest to historians of the Vietnam war as they include conversations between Nixon and Henry Kissinger, his national security adviser.

The two men discuss how to deal with an increasingly awkward South Vietnamese ally, President Nguyen van Thieu, as the US seeks a peace deal with North Vietnam.

On 9 January, Nixon's birthday, Kissinger sent word from Paris that so much progress had been made in negotiations that he believed a settlement was imminent. The tapes provide a glimpse of Nixon's reaction.

Altogether, about 154 hours of tape recordings from the Nixon White House were released today, along with 30,000 documents. The famously paranoid Nixon started secretly taping conversations and telephone calls in several locations, including the Oval Office, his office in the Old Executive Office building, the cabinet room, and Camp David in 1971.

There are 2,217 hours of tapes containing conversations through to July 1973 available to the public.