The White House said yesterday that President Carter was unaware at the time of overtures earlier this month by Central Intelligence Director Stansfield Turner to Sen. Dick Clark (D-Iowa) about possible covert U.S. military aid to rebels in Angola.

"The president had no knowledge they were doing this sort of thing," the White House press secretary Jody Powell said yesterday, referring to Turner and David Aaron, Carter's deputy national security affairs adviser, both of whom talked to Clark earlier this month about the Angola situation.

Powell added that it was his "impression" the president did not learn of the Clark discussions until Tuesday night, after reporters had raised questions about them.

Authoritative sources added yesterday that senior White House aides who felt they should have known about the Tuner meetings with Clark had no inkling of them until Tuesday night.

The Washington Post reported yesterday that Aaron in vague terms and then Turner in specific terms talked to Clark about the United States transferring military aid through a third country to the United Front for the Total Independence of Angola (UNITA), a rebel faction fighting against Angola's leftist central government.

Clark is the author of a legislative rider forbidding any direct or indirect U.S. aid to Angola without expressed congressional authorization. Some members of the Carter administration, including national security affairs adviser Zbigniew Brzezinzki, have been discussing the idea of aiding UNITA rebels in hopes of tying down Cuban troops in Angola, so they could not easily move to another African country like Rhodesia.

The Post learned yesterday that as long as a month ago Brzezinski discussed this idea with some senators. It is known that Brzezinski has been looking for many weeks for some gesture or new policy the United States could use to respond to Cuban and Soviet intervention in Africa.

Powell's denial that Carter knew anything about approaches to Clark earlier this month raised the possiblity that Brzezinski, his deputy Aaron and Turner were operating on their own in searching for some way to take action in Africa. Reliable sources have said that senior State Department officials strongly opposed any new U.S. initiative in Angola.

Senior Carter administration officials met at the White House yesterday to thrash out a new policy statement on Africa to try to clear up the questions raised in recent days. Carter is expected to reveal the fruits of this meeting at a press conference in Chicago today.

There are officials in the administration, according to reliable sources, who argued as recently as yesterday that Carter ought to seek repeal of the Clark amendment, but apparently this view did not prevail in yesterday's discussions.

Powell yesterday portrayed the meetings between Aaron, Turner and Clark as "a reasonable and routine thing to do" in light of U.S. concern over Soviet-Cuban penetration in Africa to discuss "possibilities" for American responses.

Powell said explicitly that the two administration officials were not sent to Clark to run specific proposals by him.

However, reliable sources said yesterday that Turner showed Clark a memorandum with specific numbers and types of weapons to be supplied to UNITA through intermediaries. Turner, it is said, observed that this plan appeared to conflict with the Clark amendment banning any form of aid to Angola.

Clark reportedly agreed with this judgement, eventually telling Turner that there was no way such aid could be given consistent with the law. Turner ultimately agreed with this legal judgment.

A source raised the question of whether Turner could present a detailed plan for aid to UNITA without the president knowing about it.

In describing the Aaron and Turner contacts with Clark yesterday as informal examples of "talking to people on the Hill," Powell said he wasn't even sure that Aaron knew of Turner's visit to Clark.

However, a source said yesterday that when Turner first saw Clark, he said he had come to expand on matters that Aaron had raised with the senator on his earlier visit.

Additionally, it was learned yesterday that Turner's visit to Clark followed an earlier consultation between the CIA director and a senior member of the Senate Intelligence Committee. That senator told Turner, it was learned, that if he hoped to build Senate consensus for new aid to UNITA, Clark's acquiescence would be necessary. This senator urged Turner to talk to Clark.

Turner later reportedly Clark's opposition to any new aid for UNITA to a meeting of the National Security Council which Carter did not attend. Shortly after that meeting, at a congressional leadership breakfast, Brzezinski responded to a question by Senator Minority Leader Howard H. Baker Jr. (R-Tenn.) that presidential hands were tied in Africa by fast congressional action.

Baker and House Minority Leader John J. Rhodes (R-Ariz.) later told the press the Carter administration was concerned about restrictions on its options in Africa, and this began a series of similar signals from the White House that have continued in the week since that breakfast.

A CIA spokesman yesterday said he would have no comment on Turner's role in these matters. The CIA spokesman referred a questioner to Brzezsiki's press spokesman at the White House.