Radziwill was witness to history in the "Camelot" White House, married a prince and counted Andy Warhol, Truman Capote and Rudolf Nureyev as friends in a star-studded life.

CBS News, citing family friend Mathilde Favier, the public relations director for Christian Dior, said Radziwill died on Friday. Women's Wear Daily had first reported the death on its website, saying it occurred at Radziwill's New York City home. The cause was unknown.

Radziwill's world was inhabited by doyennes of high society, artistic celebrities, fashion moguls and wealthy, prominent husbands - including one whose royal status made her a real-life princess. She was an actress, interior decorator, author, fashion public relations executive and television interviewer, although some of those careers were short-lived.

Radziwill was a portrait of sophistication and words such as "enchanting" and "adored" seasoned her conversations. For years she was a perennial entry on international best-dressed lists.

Caroline Lee Bouvier was born March 3, 1933, in Southampton, New York, four years after her sister, the future first lady Jacqueline Bouvier Kennedy Onassis. She was called Lee to appease a "rather unpleasant grandfather," Radziwill told the New York Times.

The Bouvier sisters were close but there was an undercurrent of competition between them. One biographer said the girls' father, the dashing John "Black Jack" Bouvier, favoured Jackie and Lee felt she could not live up to his expectations. Both girls idolised their father but Lee said she had a difficult relationship with their mother, Janet, who called her fat.

Radziwill recoiled at suggestions of resentment toward her sister, telling People magazine in 1976, "It's just the most ludicrous talk in the world that we're rivals. We're exceptionally close and always have been."

Nor did Radziwill like anyone thinking that she lived in Jackie's shadow.

"I'm nobody's kid sister," she told People.

The sisters visited often - Lee and her family had been regulars at the White House during Christmas season - until Jackie's death in 1994. They collaborated on "One Special Summer," a book about a European trip they took in the 1950s, and Jackie named her first child Caroline in honour of Lee.

Like her older sister, Radziwill attended the exclusive Miss Porter's boarding school and later went to Sarah Lawrence College.

In 1953 she married Michael Canfield, son of the president of the Harper & Brothers publishing house, and the couple moved to England. They split in 1958 and a year later she married Prince Stanislas Radziwill, an exiled Polish nobleman who invested in London real estate.

Radziwill and the prince had two children, Anthony and Christina, and lived on a street behind Buckingham Palace during what she told the New York Times was the happiest period of her life.

When John F Kennedy became president in 1961, he and Jackie, who had married in 1953, brought a new youthful mood to the US capital, giving birth to the "Camelot White House." Despite living in London, Radziwill, then known as Princess Lee Radziwill, managed to be in the thick of the Washington Camelot.

"I can't deny those few years were glamorous," she told the Times. "Being on the presidential yacht for the America's Cup races, the parties with the White House en fete. It was so ravishing."

In a 2001 interview with ABC, Radziwill told of being in the private quarters of the White House with Kennedy and her sister at the peak of the 1962 Cuban missile crisis. She said one night the president took a phone call and afterward told them, "In three minutes we'll know if we're in all-out war or not".

When her second marriage deteriorated, Lee moved back to New York and she and the prince divorced in 1974.

She was married to Herbert Ross, director of the movies Footloose and Steel Magnolias, from 1988 to 2001.

She also had a relationship with Greek shipping magnate Aristotle Onassis before he married Jackie. Radziwill described Onassis to the Times as "dynamic, irrational, cruel, I suppose, but fascinating".

In New York, Radziwill became one of Capote's "swans" - the name the writer gave to the gossipy circle of his New York socialite women friends. Capote fell out of favour with them in 1975 when Esquire magazine published "La Cote Basque 1965" - his thinly veiled tale of sex and dirty secrets based on the "swans."

Radziwill worked for editor Diana Vreeland at Harper's Bazaar magazine, did public relations for designer Giorgio Armani and was an interior decorator in the 1970s. In 1974, the CBS television network gave her an interview show, Conversations With Lee Radziwill, in which she talked with famous friends such as Nureyev but it was cancelled after six episodes.

Radziwill's son, Tony, died of stomach cancer in 1999, less than a month after her nephew, John Kennedy Jr, was killed in a plane crash.

Australian Associated Press