One of the men who helped put Democrat John Kerry (search) on the defensive over his military record during the Vietnam war is answering questions about his own service during that conflict.

During an Oval Office conversation in 1971, John O'Neill (search) tells President Nixon he was in Cambodia in a swift boat during the war — a claim that is at odds with O'Neill's recent statements that he wasn't in the country.

"I was in Cambodia, sir. I worked along the border," O'Neill is heard telling Nixon in a conversation that was taped by the former president's secret recording system. The tape is stored at the National Archives in College Park, Md.

In an interview Wednesday with The Associated Press, O'Neill did not dispute what he said to Nixon on June 16, 1971, but he insisted he was never actually in Cambodia.

"I think I made it very clear that I was on the border, which is exactly where I was for three months," O'Neill said of the conversation. "I was about 100 yards from Cambodia."

Chad Clanton, a spokesman for Kerry, said the tape "is just the latest in a long line of lies and false statements from a group trying to smear John Kerry's military service. Again, they're being proven liars with their own words. It's time for President Bush to stand up and specifically condemn this smear."

O'Neill has emerged as a leading figure in the attacks on Kerry's war record. He is co-author of "Unfit for Command," which accuses Kerry of exaggerating his military record in Vietnam. O'Neill is also a member of Swift Boat Veterans for Truth (search), a group that has aired two television commercials harshly critical of the Democratic presidential nominee.

O'Neill served in Vietnam from 1969-70 and took command of Kerry's swift boat after the future Massachusetts senator returned home from the war.

In the book, O'Neill wrote that Kerry's accounts of having been in Cambodia on Christmas Eve, 1968 "are complete lies."

He wrote that "Kerry was never ordered into Cambodia by anyone and would have been court-martialed had he gone there." O'Neill added that the Navy positioned its own craft along the border area to make sure no American vessels strayed across the border from Vietnam.

In an interview earlier this week on ABC's "This Week," O'Neill said: "Our boats didn't go north of, only slightly north of Sedek," which he said was about 50 miles from the Cambodian border.

During his AP interview, O'Neill criticized Kerry for making claims, including in the Senate, that he was in Cambodia as part of a secret war authorized by Nixon.

Said O'Neill: "I don't think I ever stated in the Senate that I was on an illegal expedition to Cambodia, or wrote article after article, or wrote 51 different things" like Kerry.

Kerry has defended his war record, though his campaign has acknowledged that he may not have crossed into Cambodia on Dec. 24, 1968, as he previously has stated.

"They were in a firefight, so that's why it sticks out in his mind. They were on the border. There were no clear markings of which side of the border they were on, so it's uncertain," said campaign spokesman Michael Meehan.

Meehan said Kerry recalls being in Cambodia at some point during his Vietnam service. "He specifically remembers being in Cambodia giving special (operations) guys a ride well into Cambodia."

For his part, Kerry has accused the swift boat group of being a "front group" that is doing Bush's dirty work.

The Bush campaign denies any involvement with Swift Boat Veterans for Truth.