Failure to agree a formula for calculating trade tariffs for agricultural products is holding up plans to allow poorer countries greater access to global markets.
With just three months to go before World Trade Organisation (WTO) states must conclude some key deals, concern is mounting about the pace of negotiations on the so-called Doha Round. And the EU is being accused of creating obstructions on the easing of agriculture tariffs for developing countries.
"We've had some very tough negotiations just now," EU agriculture chief Mariann Fischer Boel said after talks in Paris today.
"These negotiations ... were very technical but today they turned out to be very political as well."
The wrangling over an issue that would determine the level of tariff cuts on imports from agriculture-producing nations threatens to sour a meeting of trade ministers tomorrow.
Negotiators are bogged down in how to slash rich state farm subsidies, to give developing country producers a better deal, and open up markets across the globe for consumer and industrial goods and services, such as telecommunications and tourism.
The World Bank has calculated that conclusion of the round could boost global incomes by $500 billion a year, if it lowers trade barriers, particularly between developing countries.
Failure to meet the July deadline would jeopardise the chances of a draft deal for the round at the ministers' next conference in Hong Kong in December - a crucial step if the negotiations are to be completed in 2006 as planned.
The EU's trade chief, Peter Mandelson, called in an article in the Financial Timesfor WTO states to start delivering. "The time is over for bickering about which component of the negotiations moves first or fastest," he wrote.
Diplomats say the EU stands accused, particularly by Brazil, of holding up negotiations on the agricultural tariffs formula. They said that without an accord on how to convert cash value per tonne into percentages there could be no serious discussion of a formula for cuts.
That was echoed by the charity Oxfam, which said "delaying tactics" by the EU could scupper the Doha round. "It is five minutes to midnight," Jeremy Hobbs, executive director of Oxfam International said.
"They won't be able to proceed on market access until they have solved this."
The differences over what is known as the " ad valoremequivalent" (AVE) came at a pre-ministerial meeting of officials from the United States, the EU, Australia, Brazil and India.