A leader of the American Jewish Committee yesterday described as "unrealistic" the suggestion by Senate Foreign Relations Committee Chairman Richard G. Lugar (R-Ind.) that American Jews should support President Reagan's embattled proposal to sell missiles to Saudi Arabia.

David Gordis, the group's executive vice president, said the Jewish community had "indicated it would not go to battle on this issue" and that Israel could "live with" the sale.

"We are not happy about the Saudis' role; we don't share the administration's feeling that the Saudis have been helpful in the peace process. We are also deeply concerned about their support for terrorist activities . . . ," he said.

While the Jewish community has not actively opposed the sale, he said, it would be "unrealistic" to expect "active support," particularly "in view of the fact that apparently not just Jews but generally the American people are not supportive of this kind of sale."

Lugar's suggestion at a White House meeting Tuesday triggered a positive response from administration officials, who met yesterday with leaders of the American Jewish Committee during its annual meeting here.

Reagan's proposed $354 million Saudi aid package was rejected by overwhelming margins in both houses, and he is expected to veto the rejections shortly while mounting a campaign to sustain the veto in the Republican-controlled Senate.

Secretary of State George P. Shultz said yesterday, "We have talked to our friends in the American Jewish community about it right from the beginning and we will continue to do so." He told the Overseas Writers Club that Israel's security is not threatened by the sale, "but we have to think about our national security interests."

Saudi Arabia "has brought a measure of stability" to the Persian Gulf region and was "a good force" in preventing united Arab support for Libyan leader Muammar Qaddafi after the U.S. bombing of Libya, Shultz said.