The House International Relations Committee, seeking to reorient U.S. policies in Africa, took preliminary action yesterday to slash military aid Zaire and convert the proposed transition fund for Rhodesia into an aid program for the black African states surrounding that white-controlled nation.

The tentative decisions, subject to review in committee markup sessions later this week, were early indications of congressional intent to make major changes on President Carter's foreign policy proposals.

The House committee proposals, if approved by Congress could complicate the Carter administration's African diplomacy.

According to Reuter, Carter is sending Vice President Mondale to Vienna later this month to discuss U.S. policy with South African Prime Minister John Vorster. Secretary of State Cyrus R. Vance is scheduled to meet British Foreign Secretary David Owen in London late this week on Rhodesian diplomacy, and Reuter quoted administration sources as saying Mondale many may also hold talks with the British on subject.

Calling the problems in Zaire "a comlex situation." Chairman Charles C.Diggs Jr. (D-Mich.) of the Africa Subcommittee said it is "not clear" whether the incursion in Shabe province is due to the return of native insurgents who had been living in Angola or to an external invasion supported by Angola, Cuba and the Soviet Union.

Gidds also said the administration of Zaire's economy by the government of President Mobutu Sese Seko and its popularity among all elements of the country leave much to be desired.

Digg's subcommittee recommended and the full committee tentatively approved, a cut of $15 million in the $30 million in proposed new military sales credits to Zaire in the international security assistance bill now being marked up.

Another subcommittee recommendation likely to be adopted later, would bar direct or indirect U.S. aid to "military or paramilitary operations" in Zaire unless President Carter submits detailed reports to Congress declaring why such aid is important to U.S. national security.

In view of military credits already on the books and U.S. leadership in debt negotiations to save Zaire from international bankruptcy, "one hardly could say that we are turning our backs on Zaire," Diggs said. However, some Carter administration officials are fearful that the congressional action being recommended would give that impression.

The proposed $100 million U.S. contribution to the planned international development fund for Zimbabwe the African name for Rhodesia) arose from then-Secretary od State Henry A. Kissinger's attempts last fall to negotiate a peaceful transition to black majority rule.

While few details have been given, both Ford and Carter administration have denied that the fund is a "ball-out" for Rhodesian whites, maintaining that it would foster economic and social development to make the trasition easier for both races.

The House subcommittee plan tentatively approved yesterday would make the $100 million available to compensate for war-related economic losses and refugee relief to Zambia, Tanzania, Mozambidue, Botswana and after the establishment of U.S. diplomatic relations, Angola. These are the five "front-line" African nations demanding majority rule in Rhodesia and in some cases allowing Rhodesian guerrilla forces to mount raids from their soil.

The subcommittee plan also would permit funds to go to Lesotho and Swaziland, small black-ruled enclaves within South Africa.

The House committee tentatively adopted language encouraging an international fund for Zimbabwe to be created after "a firm agreement on majority rule."

The Senate Foreign Relations Committee in parallel deliberations scheduled for today, expected to adopt a "sense of Congress" statement of intention to support future $100 million U.S. participation in a Zimbadwe Development Fund. But neither committee is considered likely to approve the Carter administration's request for a $100 million authorization for the still-unformed Zimbabwe fund on the present aid bill.