JOHANNESBURG, NOV. 12 -- South Africa's defense minister, Magnus Malan, said today that if the South African Army had not intervened against Cuban and Soviet forces during the latest fighting in southern Angola, Jonas Savimbi's anticommunist rebels would have been soundly defeated.

A defeat of Savimbi's Union for the Total Independence of Angola (UNITA) would have brought southern Africa "to the brink of the abyss," eventually leading to communist domination of the region, Malan said.

Savimbi told a news conference today at his bush headquarters in southeast Angola, however, that he was "very surprised" at a South African Army statement yesterday that South African forces had intervened on UNITA's behalf.

The rebel leader said South Africa had assisted UNITA, but he refused to elaborate and insisted that the aid involved neither ground troops nor air support. He suggested that South Africa's military command was attempting to take some of the credit for UNITA's success.

UNITA displayed two Cuban Air Force officers whose Soviet-made MiG21 fighter was shot down by a U.S.-supplied ground-to-air missile in eastern Angola on Oct. 28.

One of the officers who parachuted to safety, Lt. Col. Manuel Rocas Garcia, the highest-ranking Cuban yet captured by UNITA, was reluctant to answer questions, but he denied UNITA claims that morale among the Cubans in Angola was low.

UNITA commanders said that 1,984 Angolan soldiers, 27 Soviets and 21 Cubans were killed in fighting last month and that 5,000 enemy soldiers were wounded, compared to UNITA casualties of 155 killed and 622 wounded.

Savimbi said weapons supplied by the United States, particularly antiaircraft missiles, had been "decisive" in repelling the Angolan Army offensive and predicted that government forces would be unable to launch a major attack next year.

The South African command said four South African soldiers died during a battle Monday against a brigade of Angolan troops supported by Cuban and Soviet forces with tanks, artillery, warplanes and ground-to-air missiles. The command would not say how many South African troops were engaged in the battle.

Army officials in Pretoria refused to comment on news reports from Namibia that a South African-led battalion of Angolan soldiers who left their country in 1975 suffered heavy losses in the battles with Soviet- and Cuban-backed government troops.

The Angolan government claimed yesterday that 230 South African Defense Force soldiers were killed in heavy fighting recently in southeast Angola.

Malan's remarks followed South African Defense Force Chief Gen. Jannie Geldenhuys' statement yesterday that South African troops had intervened in a "limited" way against Cuban and Soviet forces in a major counteroffensive spearheaded by Angolan forces.

The statement, the first indication by Pretoria in 10 years that South Africa has been providing more than supply and logistical assistance to UNITA, appeared to undercut further the credibility of Savimbi, who has insisted that his guerrillas did not need any help from South Africa in fighting government forces.

{The Soviet Foreign Ministry Thursday denied South African allegations that Soviet soldiers were directly involved in the fighting, Reuter reported from Moscow. A ministry spokesman labeled the allegations "falsehoods."}

The statements by South Africa's two defense chiefs signaled the beginning of a diplomatic initiative by Pretoria to force the withdrawal of the estimated 27,000 Cuban troops from Angola. The Cubans support the ruling Marxist Popular Movement for the Liberation of Angola (MPLA) in the capital of Luanda.

Diplomatic sources and South African military analysts suggested that with the reported rout of seven or more Angolan Army brigades, the balance of power in southeast Angola has shifted dramatically, possibly opening the way for talks between UNITA and the Marxist government in Luanda.

The South African initiative coincides with Savimbi's strategy of pushing a new "peace plan" under which UNITA would try to negotiate a political settlement with Luanda, ending the 12-year-old civil war that has wrecked Angola's economy and led to widespread food shortages among the country's 6 million inhabitants.

It also coincides with a call by Angolan President Jose Eduardo dos Santos for a negotiated settlement of the questions of UNITA's armed presence in southeast Angola and independence for neighboring Namibia. Namibia has been administered by South Africa since World War I.

Malan said UNITA had Angolan government forces "on the run" following last month's offensive, placing Moscow in a dilemma.

"It either had to stand by and witness the defeat of the {Angolan} forces, using Russian weapons, or it had, in desperation, to become actively involved. The present Cuban-Russian offensive indicates it opted for the latter course," Malan said.

"This, in turn, forced South Africa into a clear-cut decision: accept the defeat of Savimbi or halt Russian aggression."

He said that in addition to the four South Africans killed, an undisclosed number were wounded in the fighting.