EU Trade Commissioner Peter Mandelson and his counterpart for agriculture, Mariann Fischer Boel hosted US Trade Representative Susan Schwab and agriculture secretary Mike Johanns along with Indian Trade Minister Kamal Nath and Brazil's trade representative, Foreign Minister Celso Amorim.

At the top of the agenda are questions on trade in agricultural products that have blocked progress in the WTO's Doha Development Round, launched with great fanfare in the Qatari capital in 2001.

Negotiators are under growing pressure ahead of a June 30 deadline when US President George W. Bush's "fast track" trade authority expires.

Under current legislation, the US Congress is entitled to approve or reject trade deals signed by the administration but is unable to amend them.

Without the "fast track" provision, a Doha Round trade liberalisation accord approved by the US administration could be picked apart -- and neutralised -- by members of Congress defending constituents' interests.

Rich traders, the United States and the European Union in particular, are under pressure to slash trade-distorting farm subsidies and to lower customs duties on agricultural goods from the developing world.

Emerging market powers such as India, China and Brazil, have for their part been pressed to make their markets more accessible to industrial goods and services from developed nations.

"The trade-offs are well defined but we are not yet at the final talks stage where we could fit all the key figures into a package," a source close to the matter told AFP on Thursday.

One such figure in the agricultural negotiations concerned market access, where "work is well advanced" on formulas to establish the cost for countries that wished to protect certain categories of "sensitive products" from imports.

"The differences of opinion are still far apart but clearly defined," said the EU source.

Negotiators were also far from agreeing on the maximum percentage of farm products to be considered "sensitive" however, with the EU setting the level at eight percent while the United States would only tolerate a maximum of one or two percent.