A senior State Department official said yesterday that the Reagan administration favors black majority rule in South Africa and regards members of the militant black African National Congress as "freedom fighters" in their battle against the white apartheid regime.

Testifying before the House Foreign Affairs subcommittee on Africa, Assistant Secretary of State Chester A. Crocker was asked by its chairman, Rep. Howard E. Wolpe (D-Mich.), whether the administration supported "the creation of a system based on [black] majority rule and the protection of [white] minority rights."

"I think that's inherent from everything we've said," Crocker replied.

"Does that mean [black] majority rule?" Wolpe persisted.

"Yes," replied Crocker, who is regarded as the architect of the administration's "constructive engagement" policy toward South Africa, an effort to quietly encourage reform of the white minority apartheid system.

Wolpe and his aides said this was the first time any high-ranking administration official has publicly endorsed black majority rule in South Africa in five years of testimony before the subcommittee. However, a State Department spokesman said former U.N. ambassador Jeane J. Kirkpatrick had endorsed the principle of majority rule in South Africa in August 1984.

The spokesman said Crocker did not feel that he was "breaking new ground" in making his statement and had simply meant that a democratic constitution, which the administration has long urged the South African government to adopt, "implies majority rule with built-in protection for minority rights."

At another point, Crocker also said the administration regards the ANC's guerrillas, who have been battling South African whites for years, as "freedom fighters in the generic sense."

While administration officials have previously urged Pretoria to release imprisoned ANC leader Nelson Mandela, none has ever publicly referred to the guerrillas as "freedom fighters," a term usually reserved by the administration for anticommunist rebels in Angola, Nicaragua and Afghanistan.

Crocker's comments seem certain to anger conservative groups such as the Heritage Foundation, which were already pressing the White House to dismiss the controversial assistant secretary for African affairs because of his alleged opposition to U.S. military aid to anticommunist guerrilla forces fighting in Angola.

Crocker insisted yesterday that he favored providing "effective and appropriate" U.S. aid "in every sense" to the Angolan rebel leader, Jonas Savimbi. But he again made it clear that he believed his pursuit of a negotiated settlement in southern Africa's many disputes should be regarded as one form of support for Savimbi and his cause.

Crocker was also unusually harsh in his criticism of South Africa on other issues. For instance, he denounced as "a sham" the white government's offer to negotiate with black South Africans while at the same time imposing restrictive "banning" orders on two black leaders.

The United States "condemns in the strongest possible terms" the banning orders imposed Tuesday on Henry Fazzie and Mkhuseli Jack, moderate leaders of the United Democratic Front in Port Elizabeth, Crocker said. The orders, which last for five years, restrict the two men to the city during the week and confine them to their homes on weekends.

Crocker said Fazzie and Jack were "the kind of leaders who can help defuse racial tensions in South Africa. For the South African government to state that it wants negotiations with black leaders and then to put under banning restrictions people who have to participate in those negotiations is a sham," he said