The Soviet Union's continued silence on the whereabouts and condition of dissident Andrei Sakharov is seen as a sign that he is either seriously ill or flatly refusing to cooperate with the authorities.
Moscow has imposed an effective blackout on news about the Nobel Peace Prize-winning physicist and his wife, Yelena Bonner, for more than two months despite enormous international pressure for information.
The vacuum has been filled by a variety of rumors in Moscow, some of them asserting Dr. Sakharov is dead, others that he is being given mind-altering drugs in a Soviet clinic. Dr. Sakharov launched a hunger strike on May 2 in an effort to gain permission for Mrs. Bonner to go to the West for medical treatment.
The only official word has come in occasional bland assurances by Soviet officials to visiting Westerners that he is ''quite all right'' at his home in Gorky. Western diplomats here say that sounds highly implausible.
''The pressure for news about the couple has been so great that one can assume the Soviet government would have tried to defuse the issue by now by allowing them to contact friends in Moscow,'' one diplomat said.
''The fact that they have not must indicate that any news which leaked out would be embarrassing. That could mean Dr. Sakharov is seriously ill or is still involved in some kind of protest action,'' he added.
Most of the analysts said they thought it possible that Dr. Sakharov had threatened to renew his hunger strike and that he was still being kept in a clinic for this reason.
Mrs. Bonner used to be a regular conduit for news about the nuclear physicist , who was exiled to Gorky in 1980 in a bid to halt his campaigns against human rights abuses. But at the beginning of May she, too, was barred from leaving Gorky when the police told her she was being investigated on charges of anti-Soviet agitation, an offense that could bring her three years in a labor camp. Since then only one friend has managed to see the couple, and that was in early May.
''We have now had 10 weeks of silence and that can only be a cause for concern. There is every reason for apprehension about Dr. Sakharov's condition, '' a senior diplomat commented.
Others say their pessimism was partly due to the Kremlin's refusal to give even the vaguest assurances about the couple when questioned by Western visitors , including French President Francois Mitterrand.
Moscow has retaliated against Western support for Dr. Sakharov by mounting a campaign in support of jailed US Indian leader Leonard Peltier.
Peltier, who was jailed in 1976 on charges of killing two FBI agents at a shootout in Pine Ridge, S.D., mounted a brief hunger strike in April to protest conditions in his prison in Marion, Ill.
Over the past month Moscow has described Peltier as a champion of human rights who is being persecuted for his political beliefs by a tyrannical regime. Its assertions of outrage would perhaps sound a little more credible if it had shown any interest in Peltier in the past eight years.
Despite Soviet attempts to draw close parallels between Dr. Sakharov and Peltier there has been one glaring disparity: Soviet reporters have been permitted to visit him in the prison hospital and carry out interviews. The Western press has been accorded no such liberties with Andrei Sakharov for the past four years.
A few years ago activists in Moscow would have drawn up petitions of support for the physicist and maintained a steady campaign of demands for details on his whereabouts. But since May there has been no sign of any internal Soviet protest over the affair whatever.
The silence is testimony to the success of the KGB security police in effectively smashing most organized dissidence in the Soviet capital.
The former dissident leaders, such as Dr. Sakharov, Anatoly Shcharansky, and Yuri Orlov, are all in prison or exile and most rank-and-file activists have either been permitted to emigrate or silenced by the threat of long labor-camp terms.
The only dissidents involved in anything like an organized opposition are the seven members of the ''group of trust'' which campaigns for nuclear disarmament in East as well as West. Their activities are closely observed, and attempts to stage exhibitions or collect signatures on petitions are normally stopped within minutes.
Also still active are several groups of Jewish ''refuseniks'' campaigning for the right to emigrate to Israel. But whereas the Jewish groups were once closely linked with other human rights campaigners, they now tend to focus on getting visas and on maltreatment of those who have applied to settle in Israel.
There are also no signs of new opposition groups emerging, for the younger intellectuals now take a different attitude from those of the 1960s and '70s.
Few of the younger critics of the Soviet system see much sense in staging open protests, something one Muscovite called ''tilting at windmills.''
Instead, disaffection with society now usually takes the form of ''dropping out.'' Well-educated graduates frequently opt for menial jobs as gardeners or watchmen, positions in which they are free from pressure to conform politically and are left with plenty of free time.
They air their views about the iniquities of Soviet communism in discussions behind closed doors and stop short of formulating them on paper - the step that can prompt charges of antistate agitation.
Many other disillusioned youths are turning to religion. Orthodox churchmen in Moscow report that the number of young believers who regularly attend services has rocketed in the past three or four years, despite difficulties such a step can pose to one's career.
That is a development that is not entirely unwelcome to the KGB, as it means potential rebels are channeling their energies into something that does not pose an immediate threat to the state. The churches avoid political activity as a price for their survival.