The moment he saw the Pittsburgh Symphony's concert program, Soviet Ambassador Anatoliy Dobrynin said he began to worry.

"I was afraid to turn the page," Dobrynin said later. "If the first number was 'School for Scandal' [Samuel Barber] and the second was 'Requiem' [Benjamin Britten's 'Sinfonia da Requiem, Op. 20], what was the third going to be?"

The "third," as it turned out Saturday night at the 24th annual United Nations' Concert at the Kennedy Center, was Hector Berlioz's "Sinfonie fantastique" (Op. 14a), including the movement that Dobrynin jokingly called "The Witches' Dance" (actually "Dream of a Witches' Sabbath"), a reference to Washington diplomatic maneuvers, perhaps.

After all, present at the concert and later at a dinner dance at the Sheraton Washington Hotel were nearly 140 foreign ambassadors, many of whom found the dance floor irresistible. Vice President George Bush, himself a former United Nations ambassador, appeared too busy doing the honors on the dance floor with the wives of envoys and other VIPs to have a chance to dance with his wife, Barbara.

Bush led the guest list of United States officialdom, industry leaders and envoys, and the evening's talk was as varied as the cultures and interests on hand.

Lebanon's ambassador, for example, described attending a Marine Corps ceremony at Camp Lejeune marking the first anniversary of the terrorist attack in Beirut that killed 241 U.S. servicemen.

"We're grateful for the sacrifices you, the French and multinational forces have made," said Ambassador Abdallah Bouhabib. "We, as a country, have had 125,000 killed -- when you talk about 241 to a Lebanese it may not sound like much."

Also on a lot of minds were the presidential campaigns and debates. Asked his reaction to President Reagan's promise to give U.S. "Star Wars" secrets to the Russians, Dobrynin smiled without comment.

"Well, then," a questioner persisted, "would the Soviet Union give the United States its 'Star Wars' secrets?"

"Why not?" quipped Dobrynin.

His wife, Irina, is in Moscow at the moment, so he brought as his date for the evening his granddaughter Katrina ("call me Kathy"), who said she was 15 but whom Dobrynin corrected with "she is almost 15."

Kathy has lived here at the Soviet Embassy with her grandparents since she was five months old -- her parents are divorced and her mother (Dobrynin's daughter) lives in Moscow with her second husband and their son. She explained in near-perfect English that "he always invites me. I think I'm too young to go. He dragged me into it."

Speaking to the gathering, Bush said that the United Nations Association, the evening's host, which expected to raise nearly $400,000 from ticket sales, was "more important than ever." The UNA saluted the International Civil Aviation Organization on its 40th anniversary and commemorated the 39th anniversary of the U.N.

The UNA's work reminded Bush of a story about Winston Churchill being visited by a temperance society representative critical of his drinking habits. The chairwoman told Winnie, "We're reliably informed that if all the alcohol you've consumed during the war was emptied into this room, it would come up to here" -- chest height.

"Churchill looked at the worthy chairlady, then down at the floor, saying, 'Well, my dear lady, so little have I done and [looking at the ceiling] so much have I yet to do,' " Bush continued.

"To peace," said Dobrynin, lifting his champagne glass in a toast to his tablemates, joined by granddaughter Kathy, lifting her glass of Coke.

An equally unchallengeable idea, at least according to the polls, then came from Kathy when she was asked her opinion of the outcome of the election. Reagan?

"I think he will win," she said -- which almost seemed to be a cue, for Ambassador Dobrynin said something to her in Russian, got up and motioned her to her feet.

"He wants me to meet Bush," she explained.

On her way back from meeting Bush ("a nice man," she said later), Kathy also met Health and Human Services Secretary Margaret Heckler.

"Kathy? That doesn't sound Russian enough," Heckler told her.

"Okay, call me Katrina," said Kathy.

"Are you her tutor and mentor?" Heckler asked Dobrynin, who replied, "Oh, yes."

"I have my own mind," said Kathy, who will return to the Soviet Union next year to attend college.

"That sounds awfully women's lib, Mr. Ambassador," said a male voice.

Heckler said: "All women have their own minds, they all do, and we must always follow our minds and our consciences. And if we listen to our silent drummers, and those who are around us may not understand at the time, we will proceed to a course and a target."

Kathy, who could pass for a typical American teen-ager, wore a gray sweater dress. Though a slight grimace passed over her face at one suggestion that she might dance with her grandfather, the impression lingered that the Soviet ambassador might someday find himself on a dance floor facing up to "Beat It" or some other melody of the moment.

With that awful prospect in mind, perhaps, the ambassador and his pretty blond granddaughter did in fact beat it out of the dinner.