Defense Minister Moshe Arens, in an announcement apparently meant as a conciliatory gesture toward the United States, said today that Israel has agreed to share with Washington the intelligence data and other information it gained during last summer's war in Lebanon.

Arens told a special news conference in Tel Aviv that a U.S. Air Force delegation is due in Israel early next month to begin collecting the information, which includes the performances of American-made weapons used by the Israelis and the Soviet-made weapons employed by the Syrians during the war.

Arens said Israel is "firmly convinced" that the information will not be passed on to third countries without consultation with Israel and that the "important information in its possession is most valuable to the U.S. and that it will strengthen and add to other security links between the two nations."

Arens, who took over as defense minister last month after serving a year as Israel's ambassador to Washington, is viewed here as more ready than most other Israeli officials to patch up the country's strained relations with the United States.

His announcement came a day after the latest flurry of charges and countercharges over the continuing incidents between American marines and Israeli soldiers in the Beirut area that have threatened a further souring of those relations.

The implication of Arens' statement was that Israel had decided to share the information with the United States, with no prodding from Washington. U.S. officials, however, said Arens' announcement largely amounted to acceptance of a proposal made to Israel last month by Defense Secretary Caspar W. Weinberger.

In Vilamoura, Portugal, where Weinberger is attending a NATO meeting on nuclear issues, an aide said, "This is an original American position and we welcome the news." The aide told Washington Post staff writer George C. Wilson that Weinberger had given Arens a one-page memo on terms of sharing information the day Arens left Washington to become defense minister.

Arens noted that his predecessor as defense minister, Ariel Sharon, had proposed an information-sharing accord to Weinberger last fall and an agreement was initialed by U.S. and Israeli officials in November. But U.S. sources said Weinberger had rejected this draft and countered with his February proposal.

Israeli sources said that Defense Ministry officials here had concluded that Israel had nothing to lose and possibly much to gain diplomatically by announcing its intention to share the information with the United States. The sources said Israeli officials were convinced that the United States already was gaining access to much of the most valuable information through a variety of intelligence channels.

The information at issue includes the techniques the Israeli Air Force used to knock out the sophisticated Soviet-made surface-to-air missiles used by the Syrians and the relative performances of the U.S.- and Soviet-made tanks that clashed during the war in eastern Lebanon.

This was the second time in six months that a senior Israeli official announced that the information Israel gained from its combat in Lebanon would be shared with its main ally and arms supplier, the United States. Last fall Prime Minister Menachem Begin made much the same announcement.

Arens made an indirect reference to this in his own announcement today by noting Sharon's proposal to Weinberger last fall.

"Since then, for the past four months, U.S. and Israeli delegations discussed the execution of the agreement," Arens said. "Since much time has passed and, meanwhile, some misunderstandings occurred regarding our willingness to put all information at the disposal of the U.S. government, we decided to start studying the information on the basis of long-existing agreements between the two nations."

Arens did not elaborate in his statement on the "misunderstandings," which took place while the United States and Israel have been engaged in diplomatic maneuvering over an Israeli troop withdrawal from Lebanon and the beginning of negotiations on President Reagan's proposals on the future of the occupied West Bank and Gaza Strip.

However, Arens' reference to "long-existing agreements" between the two countries apparently referred to Weinberger's latest proposal, which was said to be that the United States and Israel share intelligence information from the Lebanon war on the same basis that they have shared such information after previous conflicts in the Middle East.