JOHANNESBURG, SEPT. 18 -- U.S. disaster relief officials left here today for Namibia to make an urgent appeal for permission to transport emergency food aid to drought victims in territory held by American-backed rebels in southern Angola.

Andrew S. Natsios, director of U.S. Foreign Disaster Assistance, said most of the 750,000 to 1 million Angolans under the jurisdiction of rebel leader Jonas Savimbi were facing severe food shortages, with thousands starving.

"This is the worst situation in Africa in terms of population at risk," said Natsios in an interview. He said estimates of deaths from starvation on both sides in war-ravaged southern Angola varied from 3,800 to 10,000 during the first four months of this year.

Natsios and two aides returned Monday from a visit to affected villages in territory under Savimbi's control. Natsios said he had seen children who had eaten only one meal in three days.

Savimbi's National Union for the Total Independence of Angola (UNITA) had counted 523 deaths among children from malnutrition the first six months of this year in an area where there had always been adequate food, they said.

The three U.S. officials first visited Luanda for talks with the Angolan government. They said the situation in areas under its control appeared to be just as serious but more difficult to assess because of the difficulty of access.

The Namibian government estimates that 1.5 million people are at risk. But West European nations have stopped the shipment of 20,000 tons of food for lack of inland transport. Relief supplies sent earlier are still in the port of Lobito.

The U.S. government has decided to take the lead in trying to find some other way of delivering emergency food in the next two months. It has backed Savimbi's call for "peace corridors" into the affected areas but the Luanda government has rejected the plan.

The United Nations has drawn up its own emergency plan calling for the delivery of 100,000 tons of food but the Angolan government has not approved it, said Natsios. "Our plan is to press for food shipments immediately and bilaterally {from the United States into southern Angola} and then have the U.N. take it over in a few months."

The Angolan government has opposed this approach, saying it fears Washington will send arms as well as food to UNITA. U.S. officials have told the Angolans, however, that neutral monitors could be used to ensure that only emergency relief supplies are sent.

Natsios said it appeared the only hope for breaking the deadlock was to win cooperation of the Namibian government -- which earlier said it would not serve as a conduit unless Luanda approved.