Washington calls a new European Union farm-trade proposal "disappointing" and says it does not cut protective tariffs enough.
U.S. Trade Representative Robert Portman spoke Friday after consulting with top trade officials from the EU, Brazil, India and Australia.
The EU had put forward what its top officials called a "bottom line" offer to cut agricultural tariffs and domestic subsidies.
Brussels tied the initiative to similar-sized concessions on trade in services and manufacturing from major developing nations.
The World Trade Organization's 148 members are due to meet in December to consider an outline for a new global trade deal intended to boost the world economy and aid poor nations.
If the impasse on agricultural issues is not solved, the agreement that has so far taken four years of talks could collapse.
Some information for this report provided by Reuterts, AP and AFP.