Although the Soviet Union has said Jewish dissident Anatoly Shcharansky's mother, brother and other members of his family will be allowed to emigrate to Israel, the Soviets have not indicated when they will honor that commitment, according to U.S. officials.

"There is still a commitment to let his family go, but it was never given a specific time frame," said one official, who declined to be identified. "We consider it a matter of high importance and intend to hold the Soviets to it, but we can't say when something might happen."

The officials spoke Tuesday as Shcharansky, released to the West in February after eight years of imprisonment as an alleged U.S. spy, completed a 12-day visit to this country and returned to his new home in Israel.

Following Shcharansky's release in an East-West swap, the State Department said the agreement under which he gained his freedom also provided for exit permits for his mother, Ida Milgrom, 77, his brother, Leonid, and his brother's wife and two children.

At the time, department officials said they expected relatively quick action on the family's departure from the Soviet Union.

According to subsequent reports, however, the Soviets warned Shcharansky through the Israeli government that his relatives might encounter difficulties if he traveled to the United States or pursued other activities calling attention to the plight of Soviet dissidents.

While here, Shcharansky said he did not know why Soviet authorities were delaying permission for his family to leave. He added, though, that Soviet attempts to pressure him through his family would not work. In an interview last week with The Washington Post, he said:

"My brother says to me, 'I don't want you to correlate your behavior in any way with us.' "

Shcharansky's activities in the 1970s on behalf of Soviet human-rights advocates and Soviet Jews not allowed to emigrate won him international prominence almost equal to that of Andrei Sakharov, the physicist and Nobel Peace Prize laureate in internal Soviet exile.

In late 1984, the Reagan administration decided to use every opportunity to stress to the Soviets that it would regard release of Shcharansky and Sakharov as an important sign of Moscow's sincerity in seeking improved relations with the United States.

The Soviets refused to yield on Sakharov. But a year ago, they authorized secret negotiations that ended when Shcharansky walked across a bridge from East Berlin to West Berlin Feb. 11.

According to U.S. officials, Soviet insistence that he could be released only as part of a spy exchange precluded the other family members' leaving with him.