Soviet Ambassador Anatoliy F. Dobrynin said last night he doesn't know for sure whether he will stay on as ambassador to the United States, following the death of Leonid Brezhnev, "But for the time being, yes."

Dobrynin sailed through a dinner at the State Department accompanied by eddies of friends swirling around him. Everyone seemed anxious to be reassured that the recent events in the Soviet Union would not affect his position as ambassador here and as dean of the diplomatic corps. Dobrynin has been in Washington longer than any other foreign ambassador--more than 20 years.

Marshall Coyne, owner of the Madison Hotel and a local financier, said to Dobrynin, "You are the best friend that the United States has from the Soviet Union. You know us better than we know ourselves. It would be a terrible thing if you left."

Someone asked Dobrynin, "Is that true?"

Dobrynin laughed and answered, "Marshall Coyne always speaks the truth. At least on a narrow range of subjects."

Another high State Department official said afterward, "We certainly hope that he will stay on, and we have no reason to think that he will be replaced. He is very popular."

Dobrynin, responding to a question, said he knew the new Soviet leader, Yuri Andropov. "We have both been in the government for a long time," he said.

In the receiving line, Dobrynin was greeted warmly by Secretary of State George P. Shultz. "Two days ago you were in my country," Dobrynin said, "and now we are here together."

Dobrynin, who remained in Washington during Brezhnev's funeral, asked Shultz whether he had brought back any caviar from the Soviet Union, and the secretary said he had -- Beluga. Later, when Shultz was out of earshot, Dobrynin said he preferred salmon caviar.

Secretary of Defense Caspar Weinberger, scheduled to be a host at one of the tables, didn't make it. His wife, Jane, said that he had been in the hospital for a checkup and that he had been sent home, but the doctors told him not to go out last night. Instead, his son, Cap Weinberger, a television producer with USIA, escorted his mother.

Another ambassador whose country has been having difficulties with the United States, Fernando Schwalb of Peru, attended the dinner with his wife even though his president recently canceled a scheduled trip to the United States because of a disagreement over textile tariffs.

A film paid tribute to Clement Conger. He is curator of the State Department's diplomatic reception rooms, where the dinner was held and which the $1,000-a-plate evening benefited. Conger has raised money for antique furnishings now valued at $26 million, and the film was a surprise. Conger announced the establishment of an endowment intended to continue his efforts, "when I'm not around anymore."

Shultz said that the State Department is more fortunate than other departments because in other governmental offices, "If you try to fix up your surroundings, it's a scandal even if you pay for it yourself. But when Congress comes up here and sees all the remodeling going on I quickly say, 'I don't have anything to do with it. It's Clem's doing. It's not costing the government a penny.' And Congress looks around at what he has done, and they like it."

About 260 guests, eight of whom showed up at the last minute unannounced, attended the lavish, black-tie, seated dinner.

Seating was not according to protocol, following the inspiration of Thomas Jefferson, who advocated "pellmell" seating, roughly translated as first come, first served. The organization at the State Department was more orderly than Jefferson's -- guests drew their table assignments from a bowl as they came in.

So everyone had an equal chance to sit with a famous host: the secretary of state, Secretary of Commerce Malcolm Baldrige, National Security Adviser William P. Clark, former secretary of state William P. Rogers, Attorney General William French Smith, White House Counselor Edwin Meese, Chief of Protocol Selwa Roosevelt and the ambassadors of Great Britain, France, Egypt, Switzerland, Austria, Luxembourg, Japan, Italy, Chile and their wives at tables for 10.

Founder of the feast was Edward H. Alexander of Toledo, Ohio, president of EHA Group, a manufacturer. Alexander picked up the entire tab for the dinner, catered by Columbia (somewhere in the neighborhood of $30,000), so that all proceeds (about $235,000) went to the State Department's Americana Project.

The menu was based on the sort of food George Washington might have served at Mount Vernon (if he'd had a complete catering service), a change from similar dinners of the past that were inspired by Jefferson's taste. Conger evidently believed Washington to have been a generous and elegant host. One guest said you could tell it was a class A party because the cocktail napkins were cloth instead of paper. The menu, which began with quail eggs stuffed with caviar, went on at the table with tomato soup, a fish course of crab mornay, and then, to refresh the palate, raspberry ice, before the roast duck and wild rice and watercress salad. The finale, Charlotte Russe, was viewed by some as a gesture toward Soviet-American understanding.