JOHANNESBURG, JUNE 28 -- The United States asked the Soviet Union today to support a proposal by Angolan rebel leader Jonas Savimbi to create urgently needed "corridors of peace" to allow safe passage of emergency food to 780,000 people facing starvation in war-devastated southern Angola, U.S. officials said.

A State Department official in Washington said the Agency for International Development's office of U.S. foreign disaster assistance regards Angola as "the worst humanitarian crisis in Africa, bar none."

The disaster assistance office, which has set up a special task force to deal with the Angolan emergency, said in a June 6 report that 1.5 million Angolans, out of a population of 9 million, were affected by drought and that "many southerners are eating seeds and roots in order to stave off starvation."

The report cited an estimate by the International Committee of the Red Cross that 2,500 Angolans have died of malnutrition since the beginning of the year and that about 120,000 cattle also had perished.

U.S. officials said the situation in Angola has reached crisis proportions through the combination of a two-year drought and the steady deterioration of the local economy after 15 years of warfare between the U.S.-backed rebel forces of Savimbi and the Soviet-backed Angolan government.

One indication of the urgency of the problem, according to a U.S. official, is that Savimbi has never before asked for outside food aid for his people, having often boasted of the ability of his rebel army -- the National Union for the Total Independence of Angola (UNITA) -- to feed people in territory it controls.

Savimbi proposed the peace corridors, along with a cease-fire, in letters Wednesday to President Bush, Soviet President Mikhail Gorbachev and Angolan President Jose Eduardo dos Santos, State Department sources said.

Today, a senior official in the State Department's Africa bureau, Jeff Davidow, met with Soviet Embassy officials in Washington to broach the idea of a joint U.S.-Soviet humanitarian response to the Savimbi proposal, according to informed sources. There was no immediate Soviet reply, they said.

The Soviet Union and the United States already have joined to help get emergency food aid into war-torn, drought-stricken regions of northern Ethiopia.

In Angola, U.S. officials said, 250,000/ people are in "immediate risk of starvation," including 150,000 living in parts of southern Angola controlled by UNITA.

This area constitutes about one-third of Angola and is adjacent to Namibia and Botswana. The U.S. disaster assistance office had planned to ship 15,000 to 25,000 tons of food through these neighboring countries into UNITA territory to feed people there for one year.

But both Namibia and Botswana told the United States that they would not allow any food to be trucked or airlifted through their countries unless the Angolan government assures them that it does not object to their participation.

So far, the Angolan government has refused to give such an assurance, and the U.S. relief operation has been put on hold, sources said.

Rep. Tony P. Hall (D-Ohio), chairman of the House Select Committee on Hunger, wrote President dos Santos May 16, asking him to give international relief organizations permission to transport supplies to civilians throughout Angola "from whatever point of origination they determine is most efficient."

In his reply June 7, dos Santos indicated that his government would cooperate with donors, provided relief supplies are sent to the Angolan government and through "the appropriate national entities" responsible for distribution of such aid.

The U.S. disaster assistance office said the United Nations has issued an appeal for 38,400 tons of food to feed 780,000 "severely and critically affected persons."

The disaster assistance office has granted $1.6 million to the Red Cross to provide seeds and tools to peasants living in UNITA areas. The Red Cross is the only international relief group working in both rebel- and government-held territory.

Savimbi's idea of establishing peace corridors probably originated with a similar, successful operation two years ago in southern Sudan, where millions of people, trapped in fighting between the government and rebels, also faced starvation. After considerable international pressure on both sides, safe-passage corridors were created to allow planes to fly in food supplies, and disaster was averted.