The long-running rumor that President Bush once had an extramarital affair with a former aide burst into the media spotlight yesterday when CNN reporter Mary Tillotson asked Bush about it at a news conference carried live by her network.

A visibly angry Bush said he was "outraged" that Tillotson would ask such a question and denounced a story in yesterday's New York Post that prompted the question as "a lie."

The president took a similar tack later in the day on "Dateline NBC" when co-host Stone Phillips asked him if he had ever had an affair. Bush threatened to end the interview, broadcast last night, and told Phillips: "You're perpetuating the sleaze by even asking the question, to say nothing of asking in the Oval Office."

Unsubstantiated allegations that Bush once had an affair with Jennifer Fitzgerald, a top aide on his vice presidential staff and now the State Department's deputy chief of protocol, have been bandied about in political and journalistic circles for more than a decade. The talk was revived earlier this year after Gennifer Flowers charged in a supermarket tabloid story that she had had a lengthy affair with Democratic presidential candidate Bill Clinton.

Several news organizations, including The Washington Post and Los Angeles Times, have investigated the rumor but found no evidence to substantiate it. Fitzgerald, who was out of the country yesterday, denied the rumor a decade ago to Washington Post reporter Ann Devroy. "I spent two solid months looking into this in the early 1980s and I never found any evidence of it," said Devroy, who was then working for Gannett News Service.

The controversy marred Bush's attempt yesterday to showcase his handling of foreign policy by announcing agreement on $10 billion in loan guarantees for Israel. But it remains to be seen whether questions of infidelity will dog Bush as they did Clinton earlier this year, or blunt his emphasis on family values.

The New York Post's story -- with the banner headline,"The Bush Affair" -- was based on a footnote in "The Power House," a new book by Susan B. Trento about lobbyist Robert Gray. Democratic activists have sent the relevant passage to a number of journalists in recent weeks.

The book quotes the late Louis Fields, former U.S. ambassador to the arms-control talks in Switzerland, as saying that in 1984 he arranged for then-Vice President Bush and Fitzgerald to use a guest house in Geneva. Fields did not say he had firsthand knowledge of an affair but said the living arrangements made him uncomfortable.

The book says Fields gave the account in 1986 to former CNN investigative reporter Joe Trento, the author's husband, and later repeated it to two other people. The New York Post said Bush attended the Geneva talks in April 1984, while his wife, Barbara, was on a U.S. book tour.

Fitzgerald has worked for Bush since he was ambassador to China and CIA director in the 1970s. She was the target of frequent staff complaints that she was limiting access to Bush when she ran his vice presidential office in the early 1980s. Bush named Fitzgerald his Senate liaison in 1985 and gave her the State Department post in 1989.

The Customs Service fined Fitzgerald $648 the following year for failing to declare a silver fox cape and undervaluing a fur-lined raincoat she purchased on an official trip to Argentina.

CNN's Tillotson asked Bush about the report at a news conference he held with Israeli Prime Minister Yitzhak Rabin in Kennebunkport, Maine. She told Bush she was raising the subject "because you've said that family values and character are likely to be important in the presidential campaign."

"I'm not going to take any sleazy questions like that from CNN," the president replied. "I am very disappointed that you would ask such a question of me. . . . I'm outraged. . . . I'm not going to respond other than to say it's a lie."

Ed Turner, CNN's executive vice president, said Tillotson had asked the question on her own. "It's the role of the reporter to ask questions," he said. "What comes of them determines the news value."

Richard Gooding, the New York Post's metropolitan editor, said the tabloid published the story after determining that Fields "was not a crackpot or senile." Asked if he is troubled that the key source is dead, Gooding said, "Obviously, you'd rather have a live guy."

Bush campaign spokeswoman Torie Clarke called the New York paper "below the Star and the National Enquirer."

Clinton said yesterday that he deplored the New York Post article and sympathized with Bush. "I felt for him," Clinton said. "I like him on a personal level. I like his wife. I just don't think it ought to be part of this campaign."

In April Hillary Clinton, the governor's wife, referred to rumors about Bush having had an extramarital affair in an interview in Vanity Fair and said "the establishment" had shielded Bush from any questions about it. After the article appeared, she said she had not meant "to be hurtful to anyone."

Bush's reponse at his news conference was given extensive play on CNN and radio news throughout the day, and the three major broadcast television networks last night all used stories about it.

"We wish we didn't have to deal with this," said Erik Sorenson, executive producer of the "CBS Evening News," "but if our own viewers are hearing it all day . . . we sort of have a responsibility to address it."