(POTSDAM) - Crunch talks between four key players in the World Trade Organization -- the United States, the European Union, Brazil and India -- on a global trade deal broke down Thursday, Brazilian Foreign Minister Celso Amorim said.

Amorim said the Indian and Brazilian delegations had walked away from the negotiations in the eastern German city of Potsdam that had started Tuesday because they had proved to be futile.

"It was useless to continue the discussion given what was on the table," Amorim told reporters, flanked by Indian Commerce Minister Kamal Nath.

He said differences over agriculture subsidies -- the main bone of contention in the current Doha round of trade talks launched in the Qatari capital in 2001 -- was to blame for the failure of the Potsdam huddle.

The talks, which also included EU Trade Commissioner Peter Mandelson and US Trade Representative Susan Schwab, were originally scheduled to run until Saturday.

Mandelson expressed his exasperation with the impasse.

"While in Europe we are prepared to pay a lot, we cannot do it on less to nothing in return," he said.

A similar meeting last year ran aground and ultimately led to a suspension in negotiations for all of the WTO's 150 members.

Amorim had warned that the Potsdam meeting would be "decisive."

The four G4 powers represent a range of poor and rich countries' interests at the WTO. An agreement among them on the concessions needed to reduce barriers to trade in agriculture and industrial goods is regarded as essential to draw in the rest of the 150 members.

Negotiations to conclude a trade liberalisation deal, which is mainly meant to provide an economic boost for developing nations, have missed several deadlines since the Doha round was launched.

Developing countries and wealthy nations are at loggerheads over the degree of state support for agricultural markets and an acceptable level of protection against imports, primarily in the EU and the United States.

Rich nations are also looking for more concessions from developing nations on access to their markets for industrial goods or for services companies.

The WTO has been hoping to reach an agreement by the end of the year. Under the organisation's rules, it must be approved by consensus and even a single dissenting voice can block it.

Agreement between the G4 members is seen as crucial if any final deal is to be reached.

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