The civil war in Ethiopia has led to attacks on food convoys as well as political favoritism in the channeling of emergency American food aid, U.S. officials told Congress yesterday.

"There is no question that the conflict is a major reason why we are not able to deal fully with the problem in Ethiopia," M. Peter McPherson, administrator of the Agency for International Development, said in testimony before the Senate Foreign Relations Committee. McPherson said that the disruptions could mean starvation for additional millions of Africans.

McPherson was joined by Chester A. Crocker, assistant secretary of state for African Affairs, and Daniel G. Amstutz, undersecretary of Agriculture, in describing how fighting between Ethiopia's Marxist-oriented government and separatists in the northern provinces has made "pawns" of millions of Ethiopians suffering from famine in the drought-stricken, East African nation.

They testified as Sen. Richard G. Lugar (R-Ind), presiding at his first hearing as the committee's new chairman, attempted to expedite Senate action on President Reagan's request for additional aid that would bring the U.S. commitment to famine relief in 28 drought-stricken African countries to more than $1 billion.

McPherson said government forces and dissidents have attacked trucks carrying relief supplies to famine victims. He also said that the Ethiopian government's recent seizure of 6,000 tons of food on an Australian relief ship apparently was intended to prevent the cargo from reaching two northern provinces where the separatists are strong.

"It is just unconscionable. The starving people cannot be pawns," McPherson said. "The conflict has made it particularly difficult to move food around."

Crocker, who noted that more than half of U.S. aid to Africa this year has gone to Ethiopia, added: "We have done this in a country whose government over several years has been openly hostile and which until recently sought to hide the magnitude of this disaster from its own people. As a result, we are not in the best place to bring pressure to bear."

In addition, Crocker said, the United States cannot threaten to cut off its emergency aid because that would cause even more starvation. Instead, Crocker continued, the United States intends to work with other donor countries to put pressure on the Ethiopian authorities and to call on U.N. Secretary General Javier Perez de Cuellar to intervene "as forcefully as possible" with the Ethiopians.

McPherson, noting that the stream of refugees from Ethiopia into neighboring Sudan has raised the possibility of the famine spreading there, announced that the United States will provide Sudan with an additional 200,000 tons of food worth $47 million. That will double the amount of food aid provided to the Sudan during the present fiscal year.

McPherson also said the United States will provide additional food aid to other countries: Mali, 13,900 tons worth $7.3 million; Burkina Faso (formerly Upper Volta), 21,300 tons valued at $8.7 million; Niger, 17,900 tons worth $6.5 million and Mozambique, 3,700 tons worth $1.7 million.