"There's freer trade for industrialized countries but it is increasingly difficult for food exporting countries," Pratini told a ministerial meeting of the 10-member country Cocoa Producers' Alliance.

"We must adopt a firm and united stance," Pratini said, pointing to a growing arsenal of non-tariff trade barriers, notably plant and animal health rules.

Environmental concerns have also been exploited as an excuse to erect barriers to trade, he added.

"The last Uruguay Round was a complete failure in agriculture," he said, urging a real reduction in market-distorting domestic farm subsidies and effective implementation of trade preferences for poor countries.

Pratini singled out U.S. government loan deficiency payments for its soybean farmers which encouraged production and depressed world prices, which he said resulted an estimated $1.2 billion in lost revenue for Brazilian farmers.

Brazil, the world's second largest soybean producer after the U.S., has complained to the Geneva-based WTO about U.S. soybean subsidies.