Rhodesian nationalist leader Joshua Nkomo toughened the anti-U.S. tone of his opposition to an internal solution to the Rhodesian crisis yesterday while a black leader in Salisbury said that approach has a chance of being recognized by Britain and the United States.

Nkomo, a leader of guerrilla forces based in Zambia, said in Lusaka that the U.S. and British attitude in failing to denounce the internal approach to a solution was racist. He asked for clarification from Washington.

"Are we now going to say that the United States is a party to the opposition in Zimbabwe?" Nkomo asked, using the African name for Rhodesia. "We want to know whether the Americans are now part of the dispute with us." The internal approach excludes forces outside the country from a role in transition to black rule.

In Salisbury, the Rev. Ndabaningi Sithole briefed participants in talks between blacks and the white-minority government, describing his recent meeting with British Foreign Secretary David Owen.

Sithole said outside recognition could come even from much of black Africa if the proposed transitional administration is dominated by blacks. This is one of the questions impeding a full accord in the Salisbury talks, which reportedly made no progress during yesterday's two-hour session.