Exiled Soviet dissident Andrei Sakharov spoke with relatives in the United States today for the first time since his arrest nearly six years ago and confirmed that his wife, Yelena Bonner, will be allowed to seek medical treatment soon in the West.

The "very emotional" conversation took place during a 24-minute telephone call from Sakharov's stepchildren in Newton, Mass., to Gorky, the closed Soviet city where he is held under virtual house arrest. Soviet authorities never had allowed such calls.

Sakharov's son-in-law, Yefrem Yankelevich, said the physicist apparently began a hunger strike in early October in an effort to force the Soviets to give his wife an exit visa. Yankelevich said it appeared that Sakharov had been hospitalized for a time and was sent home Oct. 23, one day before Bonner was notified that she could leave.

Bonner suffers from glaucoma and a worsening heart condition. Yankelevich said Bonner told him that she intends to fly to Italy "at the end of the month" to consult doctors who treated her glaucoma there in the 1970s. She then will fly to Boston and may undergo heart surgery there.

The Kremlin has come under increasing pressure from the West to allow Bonner to travel abroad as a humanitarian gesture before President Reagan and Soviet leader Mikhail Gorbachev meet in Geneva later this month.

Yankelevich said that the Sakharovs seemed in good spirits, but that the 64-year-old physicist apparently lost about 20 pounds during his hunger strike. Sakharov, who is considered the "father" of the Soviet hydrogen bomb and who won the 1975 Nobel Peace Prize, also suffers from a heart ailment.

Yankelevich said the only problem Bonner mentioned was her husband's heart.

"It is not in good shape, worse than before," Yankelevich said.

"They were both very excited, as were we, when the call went through," Yankelevich said. "Dr. Sakharov was on the phone just a few minutes. We were afraid they wouldn't let him speak, so he waited until last."

Bonner, a physician and a founding member of one of Moscow's most important human rights groups, "will go to Moscow to pick up her international passport at the end of the month," Yankelevich said. "We agreed to talk again Nov. 18 to know her final plans. It was a very emotional conversation."

Bonner's two children -- Alexei and Tatanya, Yankelevich's wife -- and her mother, Ruf, live in Newton. They emigrated from the Soviet Union some years ago.

Sakharov was arrested in 1980, after more than a decade of outspoken advocacy of human rights in the Soviet Union. His criticisms of Soviet internal repressions brought him worldwide recognition. As a longtime member of the prestigious Soviet Academy of Sciences, he was immune from direct reprisal.

But when he advocated an American boycott of the 1980 Moscow Summer Olympics in retaliation for the Soviet invasion of Afghanistan, he was arrested, stripped of his honors and confined to Gorky. Since then, few outsiders have been allowed to visit and his scientific work was interrupted. Bonner was confined to Gorky last year.

Yankelevich said today that several of Sakharov's colleagues had been allowed to visit him in April and that more visits might be allowed during Bonner's absence.