Former U.S. Sen. Bob Kerrey on Thursday spoke of his "sense of anguish'' over his role in a 1969 combat mission in Vietnam that left at least 13 unarmed civilians killed, while Pentagon officials left open the possibility of a review of the case.

"I feel guilty because of what happened, not because of what we intended to do,'' Kerrey, now president of the New School University in New York, told reporters at a New York press conference. "My guilt is connected to the nature of the Vietnam War."

Kerrey, 57, a former governor and two-term senator from Nebraska who was once one of the Democratic party's leading figures, also announced on Thursday that he would not run for president in 2004. He would not say his decision to stay out of the race was related to the firestorm over the Vietnam revelations.

Kerrey was awarded a Bronze Star for his role in the incident, in which U.S. military records show that 21 enemy Viet Cong soldiers were killed during a nighttime raid on a small village. Kerrey, who said yesterday he had not considered returning the Bronze Star, has admitted in recent days his troops found no enemy troops in the village that night.

Kerrey, insisting he never set out to kill innocent people, also vigorously denied charges the mostly women and children who were killed in the incident were deliberately shot dead. One member of Kerrey's military unit has charged the former senator ordered the killings in an effort to protect his soldiers from giving away the troops' location to the Viet Cong.

Kerrey's role in the case came to light as the result of a joint investigation by The New York Times magazine and CBS News' 60 Minutes II television program.

"For more than three decades I have carried this deeply private memory with a sense of anguish that words cannot adequately convey,'' said Kerrey, who had previously spoken about the incident in a number of broadcast interviews.

In Hanoi on Thursday, the Vietnamese government said Kerrey had been remorseful in his statements about his past service in the Vietnam War and called on him to help heal the wounds left over from the conflict.

In Washington, meanwhile, Pentagon officials left open the possibility of an investigation into the awarding of the Bronze Star.

Rear Adm. Craig Quigley said he did not believe Defense Secretary Donald H. Rumsfeld was reviewing the matter, and the Pentagon spokesman said he could not say if the Pentagon would look into it. But that remained a possibility.

Asked whether it was possible that the matter would be investigated, Quigley replied: "Sure." He said he was not certain how a Pentagon investigation would be initiated, but said that it could be ordered by the Secretary of the Navy.

"I don't think it has a particular necessary starting point," he said.

Quigley did not comment directly on the Kerrey case but was asked by a reporter what obligation a member of the armed forces has to state accurately the circumstances in combat on which awards are based.

"I think that obligation is always present," Quigley said. He also was asked what are the consequences of failing to report the facts.

"You'd have to ascertain the circumstances under which the facts were put down incorrectly," he said. "Is this an honest effort to describe facts as you best remember them, and you have a failure of your memory, or conflicting facts; or is this an intentional effort from the get-go to describe a situation that never occurred? You'd have to ascertain which one you have."

Quigley was asked what would happen if it were determined that falsehoods were reported intentionally to justify a combat medal.

"Eventually, by some mechanism, you would have the award of that decoration rescinded," he said.

But "the citation is different than what we reported" to military superiors, Kerrey told the Omaha World-Herald in an interview published Wednesday.

"I lived with this privately for 32 years," he said. "I felt it best to keep this memory private. I can't keep it private any more. My conscience tells me some good should come from this."

He talked about the raid publicly for the first time last week in a speech to ROTC students at Virginia Military Institute in Lexington, Va. He said he decided to give his account after hearing that another member of his squad was offering a different version.

"I went out on a mission and after it was over I was so ashamed I wanted to die," Kerrey told The Wall Street Journal in an interview published Wednesday. "This is killing me. I'm tired of people describing me as a hero and holding this inside."

He received the Medal of Honor for a separate mission.

Kerrey ran for the Democratic presidential nomination in 1992 and served two terms in the Senate after one term as governor.