D.C. City Council member John Ray (D-At large) yesterday urged Mayor Marion Barry to consider terminating the contract between the city's new convention center and its food service operators because the controlling firm is part of a conglomerate with business in South Africa.

The convention center last year awarded its exclusive food service contract, worth $20 million to $40 million,to a joint venture controlled by Sportservice Corp., a Buffalo-based firm, after efforts to award the contract to a minority-controlled business failed.

"I am dismayed that this contract, which was supposed to go to a minority-owned firm, has ended up in the hands of a company whose South Africa operations encourage apartheid and contribute to the continuing repression of that nation's black citizens," Ray said in a letter to Barry.

Sportservice is a wholly owned subsidary of a food conglomerate called Delaware North Companies, Inc. Another wholly owned subsidary of Delaware North is part of a joint venture that holds the food service contract at Jan Smuts Airport in Johannesburg.

Sam Gifford, a spokesman for Sportservice's parent company, said yesterday that all of the company's restaurants, cafes and other facilities at the Johannesburg airport are integrated, which was a decisive factor behind the company's decision to begin operations there in 1981.

He said the company felt it was a good business decision to move into South Africa and also saw it as an opportunity to provide jobs to black South Africans.

However, Ray, who has introduced legislation that would prohibit the D.C. government from dealing with firms that do business in South Africa, said in an interview that he believes Gifford's point is irrelevant since the airport is controlled by the South African government.

Edward A. Singletary, chairman of the center's board, said yesterday the board was unaware of the South African business operations of Sportservice's sister company, and said he would direct the center's staff to look into the matter. The board has signed a 10-year contract with Sportservice and its minority partner, Waters Catering Service Inc. of Rockville, a black-owned company.

Last August, after the board selected Sportservice, board members were surprised to learn that in 1972 Sportservice's parent firm, then called Emprise Corp., had been convicted on a federal conspiracy charge involving a loan to two Detroit Mafia figures. The board was later assured that the case had no bearing on the company's current operations, which include food concessions at sports and convention centers and airports, including National Airport.

Last week, three other City Council members criticized center officials for permitting Sportservice to purchase food and other supplies for the center from firms outside the District. Sportservice's spokesman said the company is making every effort to use D.C. firms.