Prime Minister Menachem Begin pledged tonight that Israel will share with the United States the military intelligence it gained during the war in Lebanon.

In what appeared to be part of an overall effort to improve the strained relations with the Reagan administration, Begin told more than 1,000 Americans from the United Jewish Appeal that an "Israeli invention" had been the key to Israel's ability to destroy Syria's Soviet-made surface-to-air missiles during the war.

"We shall share what we discovered with our American friends," he said. "And this invention may influence the future of free nations, and we hope they recognize the service we have rendered to them."

Israeli officials have referred in the past to new equipment they used against the Syrian missile batteries during the fighting in Lebanon and have promised to share it with the United States. Begin's pledge tonight was the strongest to date on the subject.

Pentagon officials who visited Israel with Defense Secretary Caspar W. Weinberger last month expressed skepticism that Israel has devised any technological breakthroughs that are unknown to the United States. Nonetheless, the subject of sharing the knowledge and intelligence gained during the war in Lebanon has been among the sources of friction between the two countries.

Begin spoke a few hours after Defense Minister Ariel Sharon invited the Reagan administration to send a delegation to Israel to inspect the military equipment Israel captured from the Palestine Liberation Organization and to review Israel's intelligence findings on the performance of Soviet-made equipment during the fighting.

With Israeli Foreign Minister Yitzhak Shamir meeting today in Washington with Secretary of State George P. Shultz, this gesture and Begin's pledge appeared to be part of a concerted effort to avoid any more friction between the two governments.

The prime minister, who was enthusiastically cheered by his American audience, said Israel "has nothing to apologize for" in the war in Lebanon. He referred only obliquely to the massacre of Palestinian refugees in West Beirut, saying that at times "tragedies happen that mar great events."

He said that criticism of Israel eventually "will pass" and pale beside the additional security the war gained for the country.

Meanwhile, sporadic fighting continued in Lebanon today. The Israeli military command announced that two Israeli soldiers were wounded during the day in exchanges of fire with Syrian troops.

Earlier today, according to Israeli radio, Begin told his governing Likud bloc partners that the United States and Israel are in "complete agreement" on necessary security arrangements in southern Lebanon. Begin reiterated Israel's opposition to the continued presence of United Nations forces in the area and charged, without elaboration, that the U.N. forces now in southern Lebanon had agreed in writing to allow Palestinian guerrillas to operate in the area against Israel, according to the report.