"There is no need to pretend that this has not been a failure," said India's Minister of Commerce, Kamal Nath, after three days of fruitless discussions at the WTO.

"We came to the conclusion that there is just not any negotiating space, because there is really a difference of perception," he told journalists, adding that he would be leaving the organisation's Geneva base later Saturday.

Brazil and India, who steer the powerful G20 bloc of developing nations, had faced off with other WTO heavyweights including Australia, the European Union, Japan and the United States, during talks which began Thursday.

A compromise among the six players is regarded as the key to resolving the near five year-old deadlock at the 149-nation WTO, because their diverse economic interests are at the heart of disputes over how to shake up world trade.

Failing to narrow differences is nothing new at the WTO.

The Doha Round has swung regularly from near-collapse to revival since it was launched in the Qatari capital in 2001 with the goal of slashing trade barriers and helping developing economies accelerate economic growth.

Negotiations were originally meant to finish in 2004, but the end-date was later pushed back to December 2006.

The specific aim of the latest meeting was to reach a deal on the mathematics for cutting farm subsidies and customs duties levied on imports of agricultural and manufactured goods. An accord on that issue is a crucial step towards a final trade treaty.