LOS ANGELES (AP) _ Neckwear once owned by Rudy Vallee is on its way to President Reagan and former Japanese Prime Minister Yasuhiro Nakasone in hopes of winning VIP support for an international art competition.

More than 600 ties from the late actor-crooner's wardrobe will be used in the promotion for the International Art Challenge, said John Schalter, who bought the Vallee tie collection for $4,500.

While the tie-in between art and neckwear may seem remote to some, Schalter said he hoped high-level interest would be a boost to next year's competition.

One tie already is on the way to Nakasone, and another, featuring a handpainted spur, will take its place under President Reagan's Christmas tree. Vallee is said to have worn the tie on a promotional tour for the 1940 movie ''Santa Fe Trail,'' in which Reagan appeared.

About 100 ties, some adorned with celebrity gravy stains, were given to artists Sunday.

The tie collection was selected from among 5,000 ties found inside a locked attic in Valle's Hollywood home shortly after the actor's death last year. The cache caused one friend to refer to Vallee as the Imelda Marcos of ties, said Chris Harris, who was Vallee's publicist.

''Rudy loved ties,'' friend Joanna Sturdza said.

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BOSTON (AP) - Retired House Speaker Thomas P. ''Tip'' O'Neill Jr. was in excellent condition Monday following removal of most of his prostate gland just two weeks after major surgery for bowel cancer, his surgeon said.

The tissue removed from the enlarged gland was benign but tests will be performed this week to confirm the initial diagnosis, doctors said.

''The speaker is doing beautifully,'' Dr. Jerome P. Richie, who performed the surgery, said after the 90-minute operation at Brigham and Women's Hospital.

''He has the strength and the character to overcome the (strain of the) second operation,'' said Richie, chief of urology at the Boston hospital and a professor of surgery at Harvard University.

The operation removed 90 percent of O'Neill's prostate gland, which surrounds the urethra. Full removal is performed only when cancer is present, Richie said. Prostate cancer is found in roughly 5 percent to 10 percent of men who have surgery to relieve the enlargement, he said.

O'Neill has suffered from an enlarged prostate for several years, he said. O'Neill is expected to be hospitalized for a week to 10 days, Richie said.

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HONOLULU (AP) - Actress Carrie Hamilton says she played Scrabble with her mother on the island of Maui while ''getting sober'' from a longtime drug habit.

Hamilton, daughter of TV personality Carol Burnett and producer Joe Hamilton, was in Honolulu for the premier of the movie ''Tokyo Pop,'' in which she stars.

Hamilton said she took ''almost every drug in the dictionary'' from the time she was 13 until she quit six years later. She said she decided to quit because she ''wanted to do something in my life.''

Hamilton, 23, said she talks about her drug problem to help other young people.

After the film premier, Hamilton planned to returned to her California home and concentrate on the book she is co-writing with her mother about their troubled past.

It is not ''a drug book,'' but a book on mother and daughter communications, Hamilton said.

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SAN ANTONIO, Texas (AP) - Country singer George Strait's white hat went for $420 and David Robinson's San Antonio Spurs jersey brought in $650 during a telethon to raise funds for needy children.

''I hope everybody donates money. It's for a great cause,'' Strait said in a taped segment Sunday on the second annual Elf Louise Christmas Project telethon.

Robinson also donated a pen he used recently to sign an eight-year contract worth about $26 million. Robinson, a former Navy center, will join the basketball team in two years after he finishes his military commitment.

The telethon raised $48,238 to buy toys for needy children and more donations continue to pour in, said Elf Louise spokeswoman Faye Borroum.