Arthur Ashe, the world's only black professional tennis player, in a speech last night a B.U. called for a gradualist, non-isolationist approach to end South Africa's system of apartheid.

Several black South African expatriates in the audience of about 600 in B.U.'s Hayden Hall charged that Ashe, by participating in the South African Open tennis tournament in 1973 and 1974 had "allowed himself to be used by the racist government in South Africa."

Ashe said that the South African government was "too strong, too much in control" for a revolution or military intervention by other African countries to succeed. "The South Africans have an Israli mentality about defending their country," he said.

Ashe said that on his second visit to South Africa, "black and white players used the same dressing rooms, barriers between black and white sections in the stands disappeared and people could sit anywhere, and all the racial placards were gone at the park,"

One of the expatriates, who asked not to be identified, said, "Exploitation of blacks will continue even when all the signs are removed. You, Mr. Ashe, have put yourself on the same side as the racist government. They want to convince the world that they are changing. They are not!"

After three expatriates had challenged Ashe, the tennis player said, "My time is up. I stand condemned."