Chase Manhattan Bank chairman David Rockefeller today disclosed that his bank lias agreed to withhold loans from South Africa that it sees as assisting that government's official policy of racial separation.

Chase thus becomes the first major U.S. bank to adopt a lending stance in explicit opposition to South African apartheid.

Responding to a comment at the bank holding company's annual shareholders meeting, Rockfeller revealed that Chase recently arrived at "a lending policy which specifically excludes loans that, in our judgment, tend to support the apartheid policies or reinforce discriminatory business practices."

The bank, third largest in the world with assets at the end of 1976 of $45.6 billion, however, still is "willing to consider loan proposals for projects of a productive nature which we believe will result in social and economic benefits for all South Africans," Rockefeller added.

Church groups have urged such a policy on most big banks that do business in South Africa, but have encountered stiff opposition from the bank managements who claim it would do more harm than good.

For example, at today's annual meeting of Citicorp, the holding company for Citibank, a shareholder resolution that the bank hold back all loans to the Government of South Africa until the government agreed to end its apartheid policy was backed by only 2.2 per cent of the votes cast, with 97.8 per cent in opposition.

Prior to the vote, Citicorp chairman Walter B. Wriston argued that there are "forces afoot for change" in South Africa, and that Citibank's continued loans in that country could prove "a positive force" to effect that change.

At the Chase meeting, Timothy Smith, speaking for the Interfaith Center for Corporate Responsibility, said his group was "very pleased" by the Chase move.

Rockfeller, responding to a question on whether the new policy in the future would bar a loan like the one Chase participated in last year to a South African government-owned utility, said he would "rather not try to anticipate on an iffy basis" loan requests.