WTO director general Pascal Lamy brought all members together to discuss the way forward for the stalled Doha round of trade talks, which remain mired in an impasse over agricultural subsidies and trade tariffs among many issues.

Multilateral talks will continue at WTO headquarters in Geneva until mid-July, at which point a decision will be taken as to whether to hold a ministerial meeting, the sources said.

The talks in Potsdam between the so-called "G4" -- the European Union, the United States, Brazil and India -- broke down on Thursday, and both sides traded recriminations as to who has to blame.

Brazil's top negotiator, foreign minister Celso Amorim, blamed the EU and US for the collapse, saying the two developed powers had arrived at Potsdam with their minds already made up on how much they were prepared to offer, and what they expected from the other two parties.

"What they agreed, they considered to be the agreement," he said.

This was denied by US officials, with Agriculture Secretary Mike Johanns telling reporters that there was no pre-summit stitch-up between Washington and Brussels.

All parties agreed with Lamy, however, that a comprehensive global trade deal was still possible despite all the difficulties.

It is "difficult but not impossible" for all 150 members of the WTO to arrive at a deal, Amorim said.

His words were echoed by US trade representative Susan Schwab, who told journalists that "we have not by any means given up on the Doha round... For now we go away disappointed, but not prepared to give up".