An Arab-American lobby group filed suit yesterday to stop U.S. military sales to Israel until that country withdraws from southern Lebanon.

The U.S. District Court action by the National Association of Arab Americans (NAAA) is based on the contention that Israel violated the Arms Export Control Act by using U.S. military equipment in its recent Lebanese operations. On April 5, Secretary of State Cyrus R. Vance reported to Congress that Israel's actions "may have" violated U.S. law, but Vance did not state a definite conclusion.

U.S. agreements with Israel permit American weapons to be used only for "internal security, legitimate self-defense" and participation in United Nations collective security operations. The policy and legal questions involved are whether the large-scale Israeli invasion of Lebanon is legitimate self-defense and, if not, what the United States should do about it.

Vance in his April 5 letter said he was not recommending that any further action be taken about the possible violation in view of the Middle East diplomatic situation and Israel's assurance that it intends to withdraw from Lebanon. The Arms Export Control Law provides that a nation may be declared ineligible for further shipments or sales if it is found to be in "substantial violation" of agreements on the use of U.S. weapons.

Prof. Hisham Sharabi of Gerogetown University, newly elected president of the NAAA, charged in a press conference that "any reasonable definition of the Israeli invasion of Lebanon cannot be but aggression. It cannot be defined by an responsible person as retaliation." The invasion was mounted shortly after a Palestinian commando raid near Tel Aviv.

Sharabi said the prime objective of the lawsuit is to obtain the withdrawal of Israeli forces from Lebanon. "We are very skeptical about Israel's intention of withdrawing from Lebanon given the fact that 11 years after the occupation of Egyptian, Syrian and Jordanian territory (in the 1967) war it continues the occupation."

The Arab group's law suit asks the government to produce a long list of documents concerning arms supplies to Israel, including agreements on the use of controversial cluster bombs. Shirabi said the cluster bombs - which can release a pail of grenade-sized weapons, each containing hundreds of steel sherds - are of particular concern.

The NAAA, claiming a membership of 1,500 to 2,000, is emerging as the Arab countervoice to the pro-Israeli political activism of Jewish Americans. NAAA officials estimated that 1.5 million to 2 million Americans are of Arab ancestry, compared to 5.7 million American Jews.

In both Senate and House committee deliberations on the proposed sale of U.S. warplanes to Saudi Arabia, Egypt and Israel, representatives of NAAA have testified along with those of the American Israeli coordinating group long familiar on Capitol Hill. This activity and the high-water marks so far of Arab American political efforts on the national scene.