In long-secret testimony, Richard Nixon swore to grand jurors that the famous gap in a White House tape was merely an accident.

The 18 1/2 missing minutes of a conversation between Nixon and his chief of staff were considered crucial in determining the president's role in covering up the Watergate scandal that drove him from office. Under oath, after he left office, he was no help to investigators probing what was said during the gap.

The National Archives and its Nixon Presidential Library released a transcript of the testimony Thursday, a rare look inside grand jury proceedings.

Nixon told grand jurors that in his view, it was simply an accident that some of the tape got erased. He claimed "I practically blew my stack" when he found out how much.