Discussions between US and European Union (EU) trade bosses have failed to overcome their differences on the core issue of agriculture.
The EU's Peter Mandelson is standing firm on the farming issue
After two days of talks to try to secure a breakthrough in global trade talks, the EU refused to offer any more concessions on agriculture.
The US wants the EU to reduce support and protection for European farmers.
Europe insists developing countries must first open up their markets to manufacturing and service industries.
"The way forward is not in trading blows in agriculture," said EU Trade Commissioner Peter Mandelson at a joint conference in Washington with his US counterpart Rob Portman.
He called on developing nations to improve their offers on non-agricultural industries, or "failing this, the round (of trade talks) will not succeed".
Agriculture remains the main stumbling block in long-running - and already long-delayed - efforts to secure a new global free trade agreement, and end the so-called Doha round of trade talks that started back in 2001.
A final deal was due to be signed at the World Trade Organization's summit in Hong Kong in December, but was postponed after agreement could not be reached.
A 30 April deadline has now been set for outline proposals.
While the US and many developing countries have blamed the EU for the ongoing impasse, Brussels has countered that it is wrongly being singled out for blame.
It has pointed to ongoing support in the US for farming sectors such as corn and cotton.