You might not expect Soviet Ambassador Anatoly F. Dobrynin to help the State Department pay its bills, especially for almost $5 million worth of remodeling to Secretary of State George Shultz's office and the department's Benjamin Franklin State Dining Room. But there was Dobrynin last night, acting as one of the hosts at an 18th-century-style feast to raise money for the project, entirely privately financed.

Dobrynin, when told Shultz's office remodeling would also benefit from the evening, seemed surprised.

"He knew," said Shultz. "But he doesn't always admit to what he knows."

Chief Justice Warren Burger told Dobrynin he had a foolproof idea for controlling the arms race. "I told Leonid Brezhnev the last time I was in Russia that they ought to let the president of the Soviet Supreme Court and myself negotiate arms control. Since we don't know anything about it, we wouldn't get all bogged down in details like some of the experts."

When guests asked Dobrynin what he thought prospects were for arms negotiation, he said: "I'm an optimist. It is my job to be optimistic."

Shultz said "time will tell" about the success of arms negotiations. As for staying on as secretary, Shultz said, "I expect to stay around and help out," but he wouldn't be pinned down as to how long.

Paying guests contributed at least $1,500 each to join in last night's conspicuous consumption in the Diplomatic Reception Rooms. The 80 guests drew table assignments from a silver bowl, giving them a chance to sit by table hosts Ambassador and Irina Dobrynin, Chief Justice Warren Burger and his wife, Elizabeth, Secretary Shultz and his wife, Helena, Brazilian Ambassador Sergio Correa da Costa and Zazi Correa da Costa, Argentina Ambassador Lucio Garcia Del Solar, Swiss Ambassador Klaus Jacobi and Titi Jacobi, Secretary of Health and Human Services Margaret Heckler, White House and State Department curator Clement Conger and Lianne Conger, and ABC News anchor Peter Jennings.

A guest at Dobrynin's table toasted the ambassador's 65th birthday, which is today. Dobrynin, in turn, held up the menu-placecard with his own name beneath a portrait of Benjamin Franklin.

"You see it's a picture of me. I'll send this back to my government and they will say I have been in the United States too long," he joked.

Shultz, in after-dinner remarks, paid tribute to the Diplomatic Reception Rooms as a peacemaker. He said that recently when he met with Soviet Foreign Minister Andrei Gromyko, "one of the best meetings I have ever had with Gromyko was in the John Adams Room here. I had learned from Ambassador Dobrynin that Gromyko is a fine historian of diplomacy. So I pointed out my favorite piece, Thomas Jefferson's desk on which part of the Declaration of Independence was written. The foreign minister was so interested. There was no apparent softening of the Soviet position, but it was helpful."

Shultz added that no secretary of state since Franklin has had as good a reputation as a shrewd bargainer. "But one did get Alaska from -- I forget just who." (From Russia, as Dobrynin acknowledged with a grin.)

Franklin, Shultz said, wrote that peacemakers must expect to receive blessings in the next world because they'll be cursed in this one.

"But if you are going to come together, you have to have give and take," Shultz said. "The one who gives a little will be cursed. Benjamin Franklin wasn't all right. I think peacemakers are honored."

The black-tie and jeweled guests, after dining on quail eggs, pheasant and trifle, previewed the Franklin room, swept up but still unfinished. "We hope for February," Conger said.

Also unfinished is raising money to pay for it. Another fund-raising dinner for 80 will be held tonight. The original estimate was just over $2 million to turn it into a late-18th-century classical room 101 feet long, 42 feet wide and 21 feet high. Now it's expected to cost $3.1 million. The secretary's suite cost has gone up from $1.25 million to $1.75 million. Shultz hopes to move back into his offices in December.