Lebanese Shiite leader Nabih Berri, the pivotal figure in efforts to win the release of 40 American hostages here, said today that he controls the fate of only "about 30 or 31 of them."

In an often rambling telephone interview on the NBC television news program "Meet The Press," Berri identified three different groups of hostages and suggested that he is powerless to release those under his control without endangering the lives of a smaller group held by the original hijackers. Three crew members, meanwhile, are under the joint control of Berri's Amal militia and the hijackers.

According to diplomatic sources in close contact with Berri, the smaller group of hostages -- who have been described as passengers with U.S. military or official passports and one or two with Jewish-sounding names -- is being held by the hijackers as a guarantee that Berri will not make any deals or compromises that they consider premature.

It was in this context that Berri responded today to a report that Israel plans to release 31 of the more than 700 detainees whose freedom is sought by the hijackers and Berri.

"It is not what we are asking for," Berri said. "We're asking for about 731, not 31." (The Israelis say they hold 766 prisoners, of whom 570 are Lebanese Shiites.)

"I agreed with the hijackers that we would release all together. If I release the 31," he said, "maybe they would kill the others." A unilateral move on his part would break his "contract with the negotiators," Berri said.

Yet there were some small signs of movement today in the deadlocked negotiations.

According to a senior European diplomat, Berri has discussed details of a face-saving formula for ending the crisis that might include the release of the American captives immediately in exchange for the subsequent release of all the Shiites held by Israel in Atlit Prison.

The diplomat confirmed that these discussions between Berri and some European intermediaries, probably Swiss, followed the general outlines of a plan published this morning in the independent newspaper An Nahar.

Quoting a Washington-based diplomat, the report said the proposed compromise called for the freeing of the American hostages as the first step. This would be followed immediately by a communique from the Reagan administration condemning all violations of international law, including hijackings and the Israelis' detention of the several hundred Lebanese captives.

According to the newspaper, within one week, the International Committee of the Red Cross would take up negotiations with Israel to release the detainees in Atlit.

Finally, the Lebanese government would take strict security measures around the Beirut International Airport and reinforce Lebanese Army positions there. Washington dismissed the report in An Nahar as a fabrication.

But the diplomat here said that it may indicate the direction in which talks have been heading. He cautioned, however, that the report itself seriously undermined any chance of success such an effort would have. The key to the solution was the lack of public linkage between the hijackers' release of the hostages and Israel's release of the detainees.

The same diplomat also said that while the large group of hostages under Amal control is definitely in west Beirut, there is a possibility that the smaller group, probably held by members of Hezbollah (Party of God), has been moved out of the city to the Bekaa Valley or locations near the city of Baalbek.

[In Jeddah, Saudi Arabia, the 45-nation Islamic Conference appealed to the hijackers to release the American hostages and stressed the "necessity" of freeing Lebanese and Palestinian prisoners held in Israel, Reuter reported.]