Soviet pianist Vladimir Feltsman's Carnegie Hall debut tomorrow night is important enough to Nancy Reagan that she's flying to New York for it. She promised Feltsman she'd be there when he played for the Reagans and their guests at a White House concert on Sept. 27.

Mrs. Reagan invited Feltsman to do the White House concert in a welcoming letter she wrote him when he arrived in Vienna in July. He had come highly recommended by the Reagans' son Ron, who first met Feltsman at the American Embassy in Moscow through then-ambassador Arthur Hartman, and also by Mike Wallace of CBS' "60 Minutes."

Wallace said later that he met Feltsman while doing a story about Soviet Jews when he and the "60 Minutes" crew were in Moscow last winter. In the course of things, Feltsman, whose wife Anna and their son were in Leningrad at the time, invited Wallace and Co. to his apartment, where he played for them. By then Feltsman was a world-famous refusenik whose father Oscar Feltsman is one of the Soviet Union's most popular establishment composers.

"You can imagine what that did to the family," Wallace says. "He was very depressed."

Wallace and the "60 Minutes" cameras will be at Carnegie Hall tomorrow night, filming a presumably happier ending to a story that will air early next year.

Of the 115 dinners being served tonight at the Reagans' state dinner for Israeli President Chaim Herzog, 18 will be kosher by preference, prepared by an outside caterer. White House chefs are taking care of the other 97 meals.

The White House fine-tuned its dinner plans by asking guests to state their preference when they RSVP'd to Social Secretary Linda Faulkner's office. An Israeli prime minister has been entertained at the White House, but Herzog's visit is the first by an Israeli head of state.

Secretary of State George Shultz, whose state luncheon invitations are almost as sought after as those to the president's state dinners, didn't offer his guests a choice. By necessity, all of State's meals are catered, and so everyone at today's luncheon for Herzog will eat kosher food. With about 225 acceptances, the lunch will be one of the largest in State Department history.

Among tonight's White House guests will be June Allyson and her husband David Ashrow; Jacques d'Amboise, artistic director of the National Dance Institute; Ralph Davidson, incoming Kennedy Center chief executive; country music singer Janie Fricke; Indianapolis 500 champion Danny Sullivan; actor Robert Young; ABC's Barbara Walters and her husband Merv Adelson, and singer Roberta Peters, who will entertain everyone in the East Room after dinner.

The party signals Nancy Reagan's return to official White House functions following her surgery for breast cancer and the death of her mother.

Chief of Protocol Selwa Roosevelt, who meets with her Soviet counterpart and the Soviet advance team tomorrow on details of Mikhail Gorbachev's visit, says the Soviet leader and his wife Raisa will be offered top-of-the-line hotel accommodations, as are all VIP guests of the U.S. government.

"We always extend the invitation," says Roosevelt. "Some countries accept, others stay at their own embassies."

Whether the Gorbachevs accept or not is anybody's guess, though the current betting is that they'll opt for their own Soviet Embassy.

What is certain is that Blair House, the president's guest house, won't be the home away from home for the Gorbachevs when they come to Washington next month.

"It isn't even furnished yet -- we're still doing construction," says Roosevelt, under whose watchful eye the house has been rising, like a phoenix, out of the debris of renovation.

Some State Department observers are relieved Blair House isn't ready. Far better to get the bugs out (no pun intended) when an old friend is your house guest than an old adversary.

Washington, however, appears ready for Soviet chic.

Meridian House is heralding an "old-fashioned Russian Christmas" that will include a 14-foot tree decorated with handmade Russian objects, a concert of Russian and American music and a series of Russian folk tale readings.

Also on tap is an exhibition of the holiday ornaments Nikita Khrushchev once gave Dwight Eisenhower, a collection that will be on loan from Eisenhower's granddaughter Susan. A recent visitor to Moscow, she paid her respects to the 70th-anniversary celebration of the Great October Socialist Revolution at the Soviet Embassy Friday night. She was escorted by Kentucky Republican Sen. Mitch McConnell.