President Ferdinand E. Marcos announced today that he is launching a last-ditch try to salvage collapsed negotiations between the Philippine government and Moslem rebels. He voiced fears that if the attempt fails, war may erupt again in the southern Phillippines.

Marcos sent his wife, Imelda, as a special envoy to Libya, where the talks with the Moro Nutional Liberation Front broke down last week.

The president said in a television interview that Libyan leader Muammar Qadaffi holds they key to a peaceful settlement.

"What we are fighting in the south is exported war. Let us admit that President Qaddafi was calling the shots all the time. It was the first time Marcos had admitted publicy that Libya was actively involved in the rebellica.

Meanwhile, both sides are preparing for renewed fighting.

The government has canceled leaves for the 50,000 military men in the south. The armed forces have asked the United States in expedite delivery of war material previously ordered, an informed source said.

[In overnight curfew was imposed in the southern city of Zamboanga Wednesday night, only nine days after it had been lifted, Reuter reported. Military sources said troops were on alert again after reports of renewed reruitment by the Moslem forces.]

Phillippine military sources said the rebels had brought in a few shipments of military supplies by boat from neighboring Southeast Asian countries.

Marcos today repeated his intention to hold a plebisclte in the south to determine how many provinces want to join a Moslem autonomous region.

In the talks that resulted in signing Dec. 23 of the "Tripoli agreement," the rebels agreed to a ceasefire in exchange for a government pledge granting them an " area of autonomy for the Moslems." Accord to the Tripoli agreement, the region would consist of the 13 provinces in Mindanao, Sulu, and Palawan.

Marcos said at that time be had not wanted to agree to the 13 provinces since only five have Moslem majorities, but that he had been pressured into it by Qaddafi.

The Moslems are opposed to a plebiscite and the issue is a major reason that the recent talks never really got off the ground.

The government argues that the constitution requires that a plebiscite be held to determine the shape of the Muslem autonomous region. The rebels counter that, under matial law, Marcos has created provinces without benefit of a popular vote.

The rebels made significant compromises in the original agreement by backing down on their demands for statehood in a federal system and agreeing to autonomy within a centralized system.

The Moslems have hardened some of their demands since the signing of the original agreement. Among the amplified demands are that Arabic be the official language of the region and that the Moro National Liberation Front Central Committee have vetopower over political decisions made by the government of the autonomous region.