Syrian troops of the Arab peace-keeping force in Lebanon have moved into the southern part of the country near the Israeli border to quell fighting between Palestinian commandos and Christian rightists, the PLO office said today.

The Syrians reportedly entered Tyre, on the coast, and Nabatiyeh, an inland town about seven miles from the Israeli border. The mainly Syrian peacekeeping force has not so far been deployed in areas near the Israeli border.

israeli Defense Minister Shimon Peres, speaking to reporters during a visit to the Dead Sea, said Israel "cannot tolerate a threat approaching its border" but that the "whole matter is still being examined." Unofficially, Israeli authorities were reported to feel that today's Syrian move did not represent a threat.

In other Middle East developments:

An Israeli Defense Ministry spokesman dismissed as "ridiculous" allegations that Israel was attempting to compete with the U.S. arms industry by requesting to co-produce the American F-16. Israel would not sell military equipment to a country "if the U.S. should indicate opposition," he said.

French president Valery Giscard d'Estaing, ending a visit to Saudi Arabia, said France and other Western European countries might be able to serve as guarantors for a Middle East peace settlement.