JERUSALEM — Prime Minister Benjamin Netanyahu has instructed his staff to begin high-level meetings with U.S. intelligence officials over accusations that Israel did not return all classified documents passed on by Jonathan Pollard.

The meetings could facilitate the convicted spy's release, Pollard's lawyer said after meeting with Netanyahu on Monday.

Meanwhile, in an important development in the United States, 60 senators sent to President Clinton a letter opposing clemency for Pollard.

California's two Democratic senators took opposing views.Dianne Feinstein signed the letter; Barbara Boxer did not.

Clinton is currently reviewing Pollard's request for a pardon. He has served 13 years of a life sentence.

Shimon Stern, the prime minister's legal adviser, and other senior officials were instructed to discuss with the U.S. administration claims that Israel did not return all of the highly secret material, including a key surveillance manual containing encryption codes.

According to an article in The New Yorker, the manual was described as so secret that it has never been mentioned in public.

Netanyahu plans to take action to combat what he sees as a disinformation campaign being waged in Washington, Pollard attorney Larry Dub said. He said the charges in The New Yorker article — that the documents were sold to the highest bidder — were a slur not only against Pollard but against the Israeli authorities.

Meanwhile, other rumors about Pollard continue to swirl in Israel. The latest one suggests that Netanyahu has now asked Clinton to put off making his decision until the impeachment hearings are over.

Netanyahu felt it would not be polite to put pressure on the U.S. president to decide when he is under duress, a source said.

Netanyahu's spokesman Aviv Bushinsky on Tuesday denied that the prime minister had requested such a deferral.

"The opposite is true," he said. "The prime minister is most grateful that President Clinton has kept his promise to review the possibility of an early release for Pollard."

At Netanyahu's Monday meeting with Dub, the prime minister reiterated his dissatisfaction with Labor Party leader Ehud Barak for failing to sign a joint letter to Clinton on Pollard. According to sources close to Netanyahu, Barak feared that Netanyahu would bask in pre-election glory if Pollard were released following the joint plea.

"Pollard was sent by the state of Israel," Netanyahu said. "This is not a political issue. Israel has to be responsible for bringing him home. We do not leave our wounded soldiers in the field."

The prime minister said Barak's signature was essential.

Barak responded on Israel Radio that the public declarations about Pollard had merely "buried him deeper." Barak said he believes in quiet diplomacy. When he met Clinton during his recent visit to Israel, Barak said, he had discussed Pollard with him.

"Most events don't take place on television, but rather through hard work on real issues with real people," Barak said without relating directly to the question of his signature.

Rabbi Alexander Schindler, a former chairman of the Conference of Presidents of Major American Jewish Organizations, said he is "bitterly disappointed" that Barak refused to sign a bipartisan plea to Clinton to commute Pollard's sentence.

"Are there no issues of national interest which transcend Israel's stormy partisan politics?" Schindler wrote in a statement received by The Jerusalem Post. "Should Pollard be allowed to languish in jail even a day longer for fear that a political opponent might gain an edge?"

Alon Pinkas, Barak's adviser on foreign affairs, said in a statement that Schindler "means very well and evidently wants only the best for Mrs. Pollard."

However, Pinkas added, "that is why he should be extra careful and thoroughly familiar with the facts and the complexities before releasing such a blunt and uncalled-for statement, especially pertaining to elections in Israel."