JOHANNESBURG, JUNE 14 -- Ford Motor Co., which has come under strong pressure from antiapartheid groups in the United States, is negotiating to sell its interest in a South Africa subsidiary, the chairman of the local branch confirmed today.

Ford would continue to supply its local affiliate, the South African Motor Corp. (SAMCOR), with vehicles, components, management and technical assistance, as well as continuing licensing of the Ford trademark here, Leslie Boyd, the subsidiary's chairman, said.

Responding to reports in the Johannesburg Sunday Star that Ford had started discussions about disposing of its 42 percent interest in the firm because of disinvestment pressure in the United States, Boyd said he was "aware of Ford's dicussions with representatives of SAMCOR's workers with a view to placing a major share of SAMCOR's shares in a trust for the benefit of all SAMCOR employes."

Ford reportedly is trying to transfer 28 percent of its stake to local employes and sell the remaining 18 percent to the giant Anglo American mining and manufacturing conglomerate, which is the majority shareholder. Anglo American would then own 76 percent of the firm.

Ford South Africa, a wholly owned subsidiary of Ford Motor Co. of Canada, merged with Anglo American's automobile division in 1985.

Black automotive workers, represented by the National Union of Metal Workers of South Africa, reportedly have rejected the proposal, fearing they would lose the protection of the company's headquarters in case Anglo American decided to reduce operations here.