.S. Secretary of the Air Force George V. Orr said today that he and the deputy assistant secretary of state for Africa, Lannon Walker, held impromptu meetings here with Mozambican President Samora Machel and Zambian President Kenneth Kaunda.

Orr is heading a 16-member delegation to the festivities celebrating the diamond jubilee of Swazi King Sobhuza II, the world's longest reigning monarch.

The meetings, both at the request of the U.S. officials, were described as the first between African leaders and U.S. officials since the American veto last Monday of a U.N. Security Council resolution condemning the South African incursion into Angola. That attack drew sharp criticism from black African states.

In the one-hour meeting today with Kaunda, the Zambian leader expressed concern about U.S. policy in Africa, which he asked to be transmitted to President Reagan, Orr said. Walker "explained our rationale behind some of our recent actions, including a vote in the United Nations, but I would not want to go as far as to say it was explained entirely to the Zambian president's satisfaction," Orr said.

The brief meeting yesterday with Machel dealt mostly with a bilateral relations, Orr said. "We are interested in improving our relations with Mozambique, and we went through an unfortunate incident some months ago, and we wanted to ascertain his reasons for that," Orr said. He was referring to the expulsion of four U.S. Embassy officials last March, when Mozambique accused them of being CIA spies.

Machel "also made a speech which was not well received in the U.S. even more recently and we wanted to talk about that and to explain that as far as the U.S. is concerned please tell us what your problems are and let's see if we can work out a little more friendly relationship," Orr said.