Bill Bradley said tonight that he had suffered four episodes of irregular heartbeat in the past month but said he did not feel it was necessary to disclose them until reporters inquired.

Although the condition is medically manageable, the announcement is certain to prove a distraction in the days before Monday's Iowa caucuses and the Feb. 1 New Hampshire primary.

Bradley, who is challenging Vice President Gore for the Democratic presidential nomination, left the campaign trail in California Dec. 10 after he forgot to take his medicine for atrial fibrillation and his heart began to beat too rapidly.

He went to a hospital but did not need treatment, and he said none of the more recent episodes required medical intervention either. His campaign said the Dec. 10 episode was the seventh since the condition was diagnosed in 1996, so the recent episodes occurred at a much faster rate.

"I confirm that I've had four episodes since then," Bradley said, surrounded by cameras outside the Masonic Temple here. "They have all been for short durations and have converted without any medical attention. And it is just the nature of the particular situation that from time to time it spins out, and it did on four separate occasions."

Bradley, 56, jammed his hands into his overcoat pockets and his breath hung in the freezing-cold air as he made a brief statement on the street before going inside for a town meeting that was part of a four-day bus tour that began this afternoon.

Atrial fibrillation is not a rare or typically life-threatening condition but can lead to stroke if untreated. Former president George Bush is among the 2 million Americans who have it.

Asked if he would reconsider whether to stay in the race, Bradley smiled and said, "What?"

"It has absolutely no impact on the race or my capacity to have a schedule or my intensity of campaigning," he said. "What you feel is your heart starts to beat faster. It's not a matter of being tired, you don't feel weak, it's just this odd sensation."

Bradley acknowledged, "It's more frequent than I've had in the past."

The former New Jersey senator and professional basketball star made his comments shortly after one of the episodes was reported on the Web site of ABC News. A reporter inquired in part because Bradley has had unexplained gaps in his schedule.

"I didn't think we needed to disclose it," Bradley said. "You don't want me to go around disclosing every time I flip out for an hour, or two hours. If I have to see a doctor, or if there has to be any medical attention given to it, you will receive, you will hear about it immediately. But otherwise, it's just the nature of being, it's the nature of the particular situation."

Bradley's campaign chairman, Doug Berman, said the episodes would have no effect on the campaign. "It's a non-event," Berman said. "This is like a headache, really. Every doctor who's looked at it says it's just a nuisance."

But Stuart Rothenberg, a leading nonpartisan political analyst, said the disclosure "will inevitably be damaging" to the campaign, especially given the timing.

"Bradley is going to be asked repeatedly about his health and his fitness to serve as president, when he wants to be talking about health care and education and his differences with Al Gore," Rothenberg said.

After Bradley went inside, Anita Dunn, his communications director, said the episodes occurred on either Dec. 27 or 28, and on Jan. 6, 9 and 16.

Dunn said Bradley had consulted a doctor by telephone but had not visited one in person. Twice in 1998, Bradley received cardioversion, an electric shock to the heart to restore its normal beat. In the Dec. 10 episode, which Bradley attributed to having skipped his medication, Procanbid, his heart regained a regular beat on its own.

Dunn said the medication allows him to maintain an aggressive exercise regimen. He has a private Stairmaster in his apartment at the Hotel Fort Des Moines, where he has lived for much of January.

Bradley has refused to release any medical history prior to 1996, citing privacy concerns.

Late tonight, he tried to make light of the day's events. As reporters and staff members packed the lobby of the Holiday Inn Express, in Burlington, Iowa, Bradley said in a serious tone, "I have another announcement to make."

The crowd hushed. "I'm going to raise taxes," he said, and the crowd broke up with laughter.

Staff writer David Brown in Washington contributed to this report.