A senior Israeli official hinted yesterday that the impasse over withdrawal of his country's troops from southern Lebanon might be resolved if an Israeli-supported, independent Lebanese force is allowed to continue operating in the area as part of the Lebanese army.

The official, who is here with Prime Minister Shimon Peres, gave that hint on the eve of Peres' meeting today with President Reagan. Peres met yesterday for 2 1/2 hours with Secretary of State George P. Shultz.

The chief topic of the White House meeting is Israel's desire for the United States to act as a mediator in finding a formula for Israeli withdrawal.

Following preliminary talks with Israel, Syria and Lebanon, U.S. officials said last week the chances for successful mediation do not appear good at this time. They said the main problem involves Israel's insistence that the South Lebanon Army, commanded by Christian Gen. Antoine Lahad, have a major role in preventing the return of Palestine Liberation Organization guerrillas to southern Lebanon after Israeli forces leave.

That idea has been rejected by Lebanese Prime Minister Rashid Karami and by Syria, whose influence in Lebanon gives it veto power over the Karami government. They have said the Lahad force must be disbanded and all security responsibilities in southern Lebanon transferred to the Lebanese army.

The Israeli official, who met yesterday with editors and reporters of The Washington Post, said Israel has no confidence in the Lebanese army's ability to halt terrorist attacks against the Jewish state, and insisted that Israel can see "no alternative" to the Lahad force.

But the official, who asked not to be identified, also noted that some brigades of the Lebanese army are dominated by Shiite Moslems or Druze soldiers loyal to their sects rather than to the central government. "It might be possible to legitimatize the status" of Lahad's force by integrating it into the army, he added.

The official did not elaborate. But he appeared to be proposing that Lahad's force be given the guise of a Lebanese army brigade while continuing to operate independently in collaboration with Israel.

Asked if Syria would agree to such an arrangement, he replied that if Syria wants Israel out of Lebanon, it "will have to contribute something to this scheme."