WASHINGTON -- Senator John F. Kerry is disputing an allegation made by a group of veterans opposed to his presidential candidacy that he never operated inside Cambodia during the Vietnam War.

In a just-published book, "Unfit for Command," the veterans said that "Kerry was never in Cambodia during Christmas 1968, or at all during the Vietnam War" and that he "would have been court-martialed had he gone there."

But the Kerry campaign said that the group, which calls itself Swift Boat Veterans for Truth, is wrong and that Kerry was inside Cambodia to drop off special forces on one mission and was at the border on other occasions.

"During John Kerry's service in Vietnam, many times he was on or near the Cambodian border and on one occasion crossed into Cambodia at the request of members of a special operations group operating out of Ha Tien," Kerry spokesman Michael Meehan said in a statement. The statement did not say when the cross-border mission took place.

At the time of Kerry's service, the official policy was that US forces were supposed to respect the territorial integrity of Cambodia, but they occasionally went inside Cambodia either secretly or in pursuit of the enemy...

For years, Kerry has said he was in Cambodia on Christmas Eve 1968. He gave a detailed view of that experience in an article he wrote for the Boston Herald in 1979. "I remember spending Christmas Eve five miles across the Cambodian border being shot at by our South Vietnamese allies who were drunk and celebrating Christmas," Kerry wrote. "The absurdity of almost being killed by our own allies in a country in which President Nixon claimed there were no American troops was very real." A similar recollection by Kerry was mentioned in a Globe biography of the Massachusetts senator published earlier this year.

The anti-Kerry veterans have said Kerry's recollection does not make sense because Nixon was not inaugurated until January 1969. But Kerry campaign spokesman Meehan said Kerry was referring to a range of time that included when Nixon was president-elect and president. During the 1968 presidential campaign, Nixon opposed a change in US policy that would allow "hot pursuit" of enemy forces into Cambodia; in March 1969 he authorized the secret bombing of Cambodia, which was followed by the 1970 invasion of Cambodia.

Kerry said in a 2003 interview that after the Christmas Eve 1968 engagement, he asked his crew to write a caustic telegram to the chief of naval forces in Vietnam, Elmo Zumwalt Jr., to wish him "Merry Christmas from the troops that weren't in Cambodia, which was us. We were."

Meehan, in his statement issued last week, described the incident this way:

"On December 24, 1968, Lieutenant John Kerry and his crew were on patrol in the watery borders between Vietnam and Cambodia deep in enemy territory. In the early afternoon, Kerry's boat, PCF-44, was at Sa Dec and then headed north to the Cambodian border. There, Kerry and his crew along with two other boats were ambushed, taking fire from both sides of the river, and after the firefight were fired upon again. Later that evening during their night patrol they came under friendly fire."

James Wasser, who accompanied Kerry on that mission aboard patrol boat No. 44 and who supports Kerry's candidacy, said that while he believes they were "very, very close" to Cambodia, he did not think they entered Cambodia on that mission. Yet he added: "It is very hard to tell. There are no signs."

Another crewmate who said he was with Kerry on Christmas Eve, Steven Gardner -- who is a member of the veterans group opposing Kerry's candidacy -- said Kerry was 50 miles from Cambodia at the time. He accused Kerry of lying about being in Cambodia or by the border. "Never happened," Gardner said.

Separately, according to Meehan's statement, Kerry crossed into Cambodia on a covert mission to drop off special operations forces. In an interview, Meehan said there was no paperwork for such missions and he could not supply a date. That makes it hard to ascertain or confirm what happened. Kerry served on two swift boats, the No. 44 in December 1968 and January 1969, and the No. 94, from February to March 1969.

Michael Medeiros, who served aboard the No. 94 with Kerry and appeared with him at the Democratic National Convention, vividly recalled an occasion on which Kerry and the crew chased an enemy to the Cambodian border but did not go beyond the border. Yet Medeiros said he could not recall dropping off special forces in Cambodia or going inside Cambodia with Kerry.