President Reagan said last night that the United States would continue to pursue its much-criticized policy of "constructive engagement" toward South Africa, despite recent actions by that country's government that threaten to jeopardize U.S. diplomatic objectives in the region.

He also ruled out a break in diplomatic relations with the white-ruled Pretoria government.

"We think we have been successful in getting some concessions there and some changes in their policy of apartheid, which we all find repugnant, and we're going to continue doing that," he said in his nationally televised news conference.

The president said he was concerned about the action Pretoria took last week in mounting a cross-border raid into the capital of Botswana to attack offices of the nationalist guerrilla movement there.

But he compared that raid to the U.S. government's current dilemma over whether to strike back at the Shiite extremists holding the American hostages in Beirut.

While saying he thought there was "no question" that the national guerrillas were also resorting to "violence" and "murdering" in their attacks on South Africans, he asked rhetorically, "Was the [South African] strike back at the people that were guilty or was it just a retaliation in a general direction" of the guerrillas?

"We don't know about that but we're very concerned about it," he said.

The president refused to describe a series of recent actions by the Pretoria government as a "setback" to U.S. policy toward southern Africa. These include setting up a "transitional government" in South African-administered Namibia on Monday, the raid last week into Botswana and the abortive attempt last month to blow up a partly American-owned oil facility in northern Angola.

"They're certainly not something that we heartily approve of," he said of these South African actions. "But whether they're something to make us break off relations with another government, I don't think that, either."