Why Soviets may let Alexeyeva go

The Soviet authorities appear to be going ahead with their surprise decision to surrender to the hunger strike of dissident scientist Andrei Sakharov and his wife.

The couple's daughter-in-law, who earlier in the day had accused the Soviets of bluffing and trickery, said on the evening of Dec. 10 that she had been summoned by emigration authorities for exit visa formalities. She was told to show up at the visa office Dec. 11 with her internal passport and two photographs.

Looking more exhausted than relieved, she told Western reporters this seemed to mean her visa had been granted, although it was unclear whether she would get it immediately.

The young Eurasian woman, Liza Alexeyeva, also said she had received fresh assurance that the Sakharovs had ended the hunger strike they began Nov. 22. Its declared aim was to gain permission for her to join Dr. Sakharov's stepson in the United States.

The head of the Soviet Academy of Sciences told Miss Alexeyeva the fast was, indeed, over, that the Sakharovs were now drinking fruit juices in the hospital where they were taken about a week ago, and that they were out of danger.

A KGB official had told her the same thing in separate meetings Dec. 9 and 10 but Miss Alexeyeva said after the second talk - and before the message from the academy director - that she suspected this was untrue.

Even after the visa summons and the message from the chief of the Academy of Sciences, a number of diplomats here found it hard to believe the Soviets would carry out their pledge to let Miss Alexeyeva leave.

The decision, disclosed to the young woman Dec. 9 by KGB official Alexander Baranov, would amount to a stunning about-face in the Soviets' position on the Sakharov protest. Also, the Kremlin has always seemed determined to demonstrate that Western criticism of human-rights policy here would have no practical effect.

Indeed, earlier Dec. 10, a visibly distraught Miss Alexeyeva told Western journalists, despite KGB warnings, that the timing of her departure would depend partly on her ''behavior'' toward foreigners: ''I think the KGB has used me. . . . This is all a bluff.''

She also expressed skepticism that the KGB would follow through with a decision, conveyed to her at a late-morning meeting, to allow her finally to travel to the Volga River city of Gorky. It is there that Sakharov has been exiled for nearly two years, where he and his wife began the hunger strike, and where they are hospitalized. The city is closed to foreigners.

Miss Alexeyeva was briefly detained Dec. 5 when she tried to travel there. Now she has been told that she can go to Gorky Dec. 14.

Bluff or not - and Miss Alexeyeva said she increasingly thought not, by late Dec. 10 - the Soviet moves would seem dramatically to underscore Kremlin concern over the Sakharov protest.

No foreign analysts expect that, as a result, the Soviets will be softer on other dissidents, or even necessarily on Sakharov if and when Miss Alexeyeva actually leaves. Some diplomats suspect the opposite effect is much more likely, that the Soviets will balance their apparent concession to the hunger strike with a new toughness toward others who rock the boat.

Indeed, even as Miss Alexeyeva was telling reporters of the visa summons, Soviet police were arresting a number of participants in what has become a traditional ''silent demonstration'' in Moscow to mark UN Human Rights Day.

But perhaps more than the barrage of ''peace initiatives'' fired off by President Leonid Brezhnev over the past year, the reaction to Sakharov's hunger strike does seem to suggest the seriousness of the Kremlin bid for better relations with the West.

No matter how the Sakharov saga ends, the fact that the Soviets have even moved toward ceding to the hunger strike is an unprecedented development undoubtedly signaling the depth of Kremlin concern over the outrage his death would cause in the West.