Unofficial Israeli sources have named a man who once worked for then-Prime Minister Menchem Begin as the Israeli intermediary who received secret U.S. documents from Jonathan J. Pollard, a civilian U.S. Navy intelligence analyst who was arrested by the FBI Thursday.

The name of the man has circulated in Israel since the weekend, and at least two major Israeli newspapers have tried to publish his name, but Israeli censorship refused to allow them to do so, according to informed sources.

The Washington Post has decided not to use the man's name, since no reliable source has tied him directly to Pollard. U.S. officials involved in the investigation into the Pollard case said yesterday that the name of the Israeli allegedly involved was not familiar to them and indicated that an Israeli official whom Pollard reportedly telephoned last week was someone other than the man being named by Israeli sources.

U.S. sources told The Post Sunday that after Pollard learned last week that the Federal Bureau of Investigation was investigating him, he contacted an Israeli official in Washington and said "the FBI is on to me." According to these sources, the response from the Israeli official was to the effect, "if you shake your surveillance, we'll see what we can do."

The man named as Pollard's contact in the stories circulating in Israel was not in Washington last week and never served in the Israeli Embassy here.

The Israeli government has said only that it is investigating the matter and has not made any statements about which officials, if any, might be involved.

The man identified as Pollard's contact worked for Begin and his successor, Yitzhak Shamir, on security matters. According to the story circulating in Israel, his alleged relationship with Pollard began several years ago when the American visited Israel.

U.S. officials stressed that it is unclear whether top officials of the Israeli government knew about any espionage activities in the United States or whether it was an unauthorized operation conducted at lower levels.

The Israeli government Sunday expressed "shock and consternation" about the incident. Prime Minister Shimon Peres also sent a message to Secretary of State George P. Shultz promising that the matter would be investigated fully and that any Israelis found to have engaged in spying against the United States would be punished.

In Jerusalem, senior Israeli officials told Washington Post correspondent William Claiborne that the country's political leadership had no knowledge of a spying operation. They said that if secret U.S. documents were accepted or purchased, it was done by persons acting contrary to longstanding, official Israeli government policy.

These statements came against a background of growing concern that the incident could have serious adverse consequences for U.S.- Israeli relations. The sources here said the State Department had told the Peres government that the United States expects an explanation of what happened before the end of this week.

In addition, leaders of American-Jewish organizations are known to have called Peres over the weekend and warned him that the matter must be clarified fully before Congress returns next week from its Thanksgiving recess. The Jewish leaders asked not to be identified. But one said he had told Peres that anything short of full disclosure of Israel's role could be "a blow to the solar plexus" of the strong support that the Jewish state enjoys on Capitol Hill.

The Jewish leaders said that their soundings in the aftermath of Pollard's arrest revealed considerable concern among members of Congress about whether Israel had breached the trust given it by the United States. However, the leaders added, all of the congressional figures contacted also said that they were reserving judgment until more is known. White House spokesman Larry Speakes said he did not expect the incident to damage U.S.-Israeli relations. "The United States has had a long and close relationship with Israel, and I would expect that relationship to continue," Speakes said.

Yesterday, Pollard's wife, Anne Henderson-Pollard, made a brief court appearance in which U.S. Magistrate Patrick J. Attridge ordered that she continue in custody without bond pending a hearing on Wednesday. She was arrested Friday and charged with unauthorized possession of classified documents.

Attridge ordered D.C. Jail officials to have a physician examine Henderson-Pollard after her attorney said she had been unable since her arrest to receive prescription drugs. Her father has said that she suffers from a stomach disorder.