Soviet authorities maintained a wall of secrecy around Andrei Sakharov, the country's foremost dissident, who was in his third day of enforced medical treatment today following a 13-day hunger strike.

Friends of the Nobel Peace Prize laureate said they had no information about his condition or whereabouts.

The official silence obscured an intense debate in the Soviet scientific community about ways to resolve the impasse between an unyielding government and the apparently equally unyielding physicist who developed the Soviet hydrogen bomb.

Liza Alexeyeva, 26, whose attempt to emigrate to the United States prompted Sakharov's protest, was detained by police yesterday when she attempted to take a train to Gorki, the city 250 miles east of here to which Sakharov is banished.

Alexeyeva reported that she had been warned against seeking out Sakharov and his wife, Yelena Bonner, who also was taken Friday to a hospital. It is believed they are both being force-fed or fed intravenously.

The argument heard here is that the government cannot appear to be yielding under pressure because that would open the doors to others to seek redress through hunger strikes.

On the other hand, Sakharov and Bonner have vowed to continue their hunger strike until the government allows Alexeyeva to join her husband, Alexei Semenov, in the United States. Semenov, Bonner's son, is Sakharov's stepson.

Since the authorities will be unable to force-feed the couple indefinitely, some diplomats believe the physicist, his wife and possibly Alexeyeva may be expelled from the Soviet Union as soon as the Sakharovs regain physical strength. In this view, Sakharov has become a major internal problem, the focal point of dissent.

The physicist's friends, however, believe that Soviet military authorities would vigorously oppose such a solution since Sakharov for many years was at the hub of Soviet military research and development programs.

Another reason cited is that the physicist has urged the United States to seek military superiority over the Soviet Union. The prospect of his testifying in Washington for new U.S. arms programs is unwelcome here.

Moscow is expected to have to take some course of action soon. There was speculation once that the only way to resolve the impasse was to expel Sakharov from the Soviet Academy of Sciences, of which he is a most prominent member.

But the academy is reportedly deeply divided, with Sakharov still commanding a great deal of prestige. The government is still believed to be unable to muster the two-thirds majority needed in the secret balloting to expel him from the country's most prestigious scientific body.

Thus the authorities' dilemma, in essence, is that they can neither permit the physicist and his wife to die on a hunger strike nor afford to yield to the couple's demands.

Sakharov, 60, was banished to Gorki almost two years ago, but Bonner, 58, remained his link to the outside world, allowed to travel between Gorki and Moscow. Sakharov continued to enjoy privileges accorded to academy members, including shopping in special stores. With Bonner in an unspecified Gorki hospital, the physicist is completely isolated.

In the United States, Reuter reported Semenov as saying nobody knows which hospital the hunger strikers had been taken to or if Bonner has been separated from her husband.

Soviet authorities have made it clear that they do not regard Alexeveya as having a valid claim to join Semenov in the United States. The two were married by proxy, which is not recognized in Soviet law. Moreover, the Soviets allowed Semenov's first wife to emigrate to the United States with their child 18 months ago under a provision allowing "family reunification." The couple was later divorced.

This, however, does not exclude the possibility that Alexeyeva would be permitted to travel if a way could be found under which the government would not be seen as having yielded unconditionally.