LUANDA, ANGOLA, DEC. 9 -- Angola's ruling party tonight approved the establishment of a multi-party system, discarded its Marxist-Leninist ideology and gave a vote of confidence to President Jose Eduardo dos Santos, allowing him to continue peace talks with U.S.-backed rebels.

Winding up its third congress since independence 15 years ago, the Popular Movement for the Liberation of Angola-Workers' Party also elected a 90-member Central Committee and a Politburo to carry this war-weary nation through peace negotiations and radical political changes that lie ahead.

The congress approved "democratic socialism" as its new ideology, allowing multiple parties to compete for the first time, direct election of the president and a large degree of free enterprise.

The changes are the most sweeping here since independence. While they still have to be voted on by the People's Assembly, the party's blessing assures approval by the legislature.

Dos Santos told the congress that the reforms were a response to what he called the "transformation" of international relations that includes an end of the Cold War, the new spirit of Soviet-American cooperation and the democratic revolution that swept away the socialist rulers of Eastern Europe.

The results of the six-day congress should facilitate an agreement with the U.S.-armed National Union for the Total Independence of Angola (UNITA), whose leader, Jonas Savimbi, said last week that he was no longer insisting on formal recognition by the ruling party and would settle for its ratification of a multi-party system at its congress here.

Savimbi's demand for recognition had been one of the main sticking points in talks underway for months between the government and UNITA on ending their 15-year-old civil war.

The 700 congress delegates approved a year-long constitutional revision process, starting only after a cease-fire in the civil war. A law allowing parties to organize would be approved early on, but elections, which Savimbi has sought within a year of a cease-fire, apparently would not take place until well beyond that time. No date was set.

Dos Santos apparently postponed adoption of a new constitution to allow UNITA to participate in drawing up new provisions, as the president had sought.

Another important issue that remains to be resolved is that of United Nations or other international monitoring of a cease-fire and elections.

Savimbi said Wednesday at his rebel headquarters in Jamba that he was ready to sign a cease-fire as soon as the ruling party's congress approved a multi-party system. But he conditioned his acceptance on the presence of international monitors.

The rebel leader said he needs such an international guarantee to compensate for what he expects to be an immediate cutoff of U.S. aid once a truce goes into effect.

The congress here represented a major turning point in the history of the ruling party, which has been one of Africa's most determinedly Marxist-Leninist and a close ally of Cuba and the Soviet Union.

Soviet arms and Cuban troops helped to bring the party to power in 1975 but Moscow is about to end its massive military assistance and the last of 50,000 Cuban troops stationed here are scheduled to leave by July. These changes have helped to focus the government's attention on the need for a political settlement with UNITA.

UNITA, which is scheduled to receive about $60 million in supposedly covert U.S. military aid this year, is also under pressure to reach a deal because its support in the U.S. Congress appears to be on the wane.