H. R. Haldeman said yesterday he would "challenge" President Nixon's explanation of the Watergate cover-up with "gloves off and no holds barred" in a book to be released this fall.

The former Nixon White House chief of staff, who has maintained public silence throughout David Frost's televist interviews, with Nixon, called reporters to his home to read them a two-minute statement but declined to answer any questions.

"For the past three weeks I have been watching the Nixon-Frost interviews and I guess lots of people have," Haldeman said, "I've avoided any comment on them because I had the hope they would clear up many of the questions that remain on Watergate. Unfortunately they did not.

"I feel now that I have to challenge President Nixon's explanation of the cover-up and that it's time to deal with many things that have been left unsaid."

Haldeman, who last Monday lost his Watergate conspiracy conviction appeal to the Supreme Court and faces prison for his role in the cover-up, told reporters that his book on Watergate would be released sometime in the fall. "I'll cover everything on the subject with the gloves off and no holds barred," Haldeman said.