Updated

The day before John Kerry (search) wrapped up the Democratic nomination for the presidency, he tried to talk the leader of Swift Boat Veterans for Truth (search), retired Navy Adm. Roy Hoffman (search), out of his now politically potent activism. It didn't work.

Hoffman told FOX News that the call came on March 15.

"I was somewhat flattered when he called me, but his mission was to get me to write down and submit what I thought was wrong in the [book] "Tour of Duty," his biography, where I thought there were mistakes," Hoffman said.

Hoffman commanded all swift boats (search) in Vietnam in 1968 and 1969. He began organizing the Swift Boat Veterans for Truth in January, which was after the Kerry authorized biography, "Tour of Duty," hit the shelves.

"I felt obligated even though I had retired from the Navy in 1978 after 35 years active duty," Hoffman said. "I thought maybe duty called again. And strictly on my own I started calling people I haven't seen for 34 years or so and I found that the troops were still behind me. So I'd been sending out a number of e-mails and making numerous telephone calls and obviously Mr. Kerry heard about it and he called me."

The Swift Boat Veterans for Truth is at the center of a controversy over just how much of Kerry's Vietnam heroism stories are true. The group's ads have fueled a firestorm of political criticism from the Kerry camp, which claims the group is directly supported by the White House.

The Bush-Cheney camp contends that while a couple of their advisers may do independent work for the group — as do some Kerry advisers for anti-Bush organizations — they don't condone the group's activities.

Just this week, Bush reached out to Arizona Sen. John McCain (search) — a Republican lawmaker who was a Vietnam POW — to get rid of all unregulated 527 groups altogether via court action or, if that doesn't work, legislative action.

Hoffman and other swift boat veterans say "Tour of Duty" exaggerates Kerry's heroism, charges other swift boat crews with military recklessness and celebrates Kerry's anti-war Senate testimony in 1971. Hoffman said Kerry asked him if he was willing to end his swift boat activism if Kerry allowed him to help correct the record in "Tour of Duty."

"I told him that I wasn't going to cooperate — that I felt very bitter about his qualifications and particularly with how he betrayed us in 1971," Hoffman told FOX News.

By Hoffman's account, Kerry placed the call the day before winning the Illinois primary. That victory secured the Democratic presidential nomination for Kerry.

"He knew that it would be a problem and that was the reason he was calling," Hoffman said, referring to his swift boat activism. "No question. I don't mean to imply he was shouting, it was a civil conversation."

Hoffman said Kerry was so concerned about the admiral's opposition that he offered Hoffman an open line to his personal staff and "Tour of Duty" author Douglas Brinkley (search).

"He gave me the phone number of his private secretary and said I could contact her at any time and said I could call Brinkley, who had already called," Hoffman said. "I declined, and said there was no need to discuss it any further. It was about a 45-minute conversation."

The account could be the first to show that Kerry long ago feared the potential impact of opposition from fellow swift boat veterans. It also may suggest Kerry was privately willing to concede errors in his authorized war biography.

"Over the course of the past months, John Kerry has talked to many of the vets he served with in Vietnam," senior Kerry adviser Michael Meehan told FOX News. "He did speak with Hoffman about that time ... . But the charge that somehow he could change Mr. Brinkley's book is an outright exaggeration."