Senior U.S. officials say that the Reagan administration, responding to intelligence reports, has asked top Israeli officials if their government or private Israeli arms dealers have again sold arms to Iran.

The Israelis categorically denied any new sales, the officials said.

"There have been reports of shipments that involve the Israelis and we have raised it with the Israeli government at the highest levels," said one administration official. Any new Israeli arms sale to Iran "is something viewed with the utmost seriousness and something we would want to nip in the bud," he said.

The Israelis have investigated the reports and told U.S. officials in the last few days "they find no evidence these reports are true," said another administration official. "The Israelis have reconfirmed their policy of no sales or transfer of arms to Iran."

The reports reaching U.S. intelligence agencies appear to be very fragmentary and none has been confirmed, according to several U.S. officials. One said the information appeared "very marginal." Another said they may involve British and Kuwaiti press reports that have "all been feeding on each other."

Assistant Secretary of Defense Richard L. Armitage was in Israel this week for scheduled talks with Israeli military officials but it was not known if he had raised this issue with them.

The administration has also questioned officials from several East European governments about reports of their possible involvement with arms sales to Iran. "Any time we get these reports we weigh in pretty strongly," said one State Department official.

The unconfirmed reports received by U.S. intelligence sources include allegations that some Israelis may have negotiated to sell up to $750 million in arms to Iran late last summer, a package allegedly including U.S.-made TOW antitank missiles, Israeli Gabriel air-to-surface missiles, F4 and F5 aircraft engine parts, tanks and jeeps.

The report alleged that the deal was executed through a third party based in Geneva, according to one administration official, but did not make clear whether the Israeli government or private arms merchants negotiated the deal. To obtain most of the items, the Israeli army normally would have to authorize their sale and make the items available from its stocks. The United States would have to approve any transfer of American-made arms.

Many of the items, however, could be available through the black market to private arms dealers, officials said.

The United States first raised the issue with the Israeli government "at the ministerial level" after hearing a report that some Israelis were involved in the sale of F4 parts to Iran. The Israeli government denied that report, U.S officials said.

The reports of renewed Israeli arms sales have been circulating for the past six weeks in the Israeli, Arab and European press, but the Israeli government has denied them and no hard evidence has surfaced to confirm them.

A number of former Israeli army officers have become independent arms dealers, making it difficult to determine whether the Israeli government itself is involved directly or indirectly.

"It's all very murky territory," said one U.S. official involved in monitoring arms sales to Iran.

United States suspicion about Israel's support of U.S. policy in the Persian Gulf was raised anew when Israel's defense minister told a Jerusalem news conference on Oct. 28 that the United States had been manipulated by Iraq into taking its side in the Iran-Iraq war.

Staff writer John M. Goshko contributed to this report.