American coffee companies paid an estimated $150 million in the first six months of the year for Ugandan coffee - the commodity that provides President Idi Amin with his principal source of foreign revenues.

Coffee, which accounts for 93 per cent of Amin's export earnings, is considered one of the main economic underpinnings of AMin's regime, along with lavish economic and military aid from some Arab and socialist countries.

The United States buys about one third of Uganda's coffee exports and most of the rest goes to Europe via routes established by the shadowy international coffee trade. The value of Ugandan coffee entering the United States in 1976 was $112 million, according to U.S. Customs records. This year, with coffee scarce and expensive all over the world, Ugandan imports have been larger in value and volume.

Almost all the major American coffee manufacturers use Ugandan coffee.

According to Advertising Age magazine's July 11 edition, the largest American coffee companies are General Foods (which makes Maxwell House, Yuban, Maxim, Sanka, Max-Pax and Brim); Procter & Gamble (which makes Folgers); Hills Brothers; Chase & Sanborn; Nestle; Borden, and Coca Cola (which makes Maryland Club and Butternut).

Officials of Maxwell House and Nestle said this week that the companies purchased green Ugandan beans either fromt he Ugandan Coffee Marketing Board, a state agency, or from some of the 15 to 20 coffee dealers based in New York City.

Jack Whiteman, Maxwell House spokesman, confirmed the purchases but said Ugandan coffee makes up "less than 5 per cent of our annual requirements."

An official of Nestle in White Plains, N.Y. who asked not to be identified, said "This is not a question for us; it's a question of U.S. foreign policy."

Rep. Donald J. Pease (D-Ohio), a member of the House International Relations Committee, has introduced a bill to outlaw release of Ugandan coffee from Customs Service warehouses.

Administration officials said the government is reluctant to adopt any such unilateral embargo now, however. At the annual meeting of the United Nations Human Rights Commission in Geneva in March, the United States supported a Canadian and British call for a public debate about rights violations in Uganda. But the move was defeated.

However, the foreign aid money authorization enacted this year forbids direct U.S. economic aid to Uganda and six other countries. The AMin regime has been described as "genocidal" by some critics.

Pease said this week that coffee is "vital in Amin's ability to maintain himself in power. The fact that U.S. companies are purchasing it in large quantities makes it possible for that floundering economy to stay afloat."

The impact of an American coffee embargo on the price of coffee domestically is a matter of controversy.

The Department of Agriculture wrote Pease-s office recently that a stopage might cause some temporary dislocations in domestic coffee markets. Slightly under 5 per cent of this country's coffee comes from the African country. And the department added that the effect of an import curtailment "would most likely not be very great."

Coffee trade sources in New York City said, however, that prices here might be affected because of the tight market. Uganda is one of the main sources of the robusta type coffee used in roast coffees. Angola, which produces a similar kind of robusta, has not fully recovered fromt he 1976 civil war, and poor weather cut coffee output in the Ivory Coast by 30 per cent. Port congestion in coffee-rich Colombia is another problem.

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Well-informed coffee dealers [WORD ILLEGIBLE] is difficult to ascertain the [WORD ILLEGIBLE] Ugandan coffee arriving at the New York City docks. Some may have [WORD ILLEGIBLE] traded in Europe. Presumably, [WORD ILLEGIBLE] smuggled beans end up in the [WORD ILLEGIBLE] of big dealers or coffee companies [WORD ILLEGIBLE] this country.