"If we don't turn things around in the next two weeks, we will not make a breakthrough this summer and then we will be facing defeat," Mandelson told reporters after three days of fruitless World Trade Organisation negotiations.

The 149 members of the WTO had given themselves until the end of June to reach an interim deal on the calculations for cutting rich countries' farm subsidies and customs duties, as well as import tariffs levied on manufactured goods by emerging economies such as Brazil and India.

But they missed their target because of persistent differences over the relative concessions required of different members, with negotiators refusing to budge unless others shifted position first.

"The key pieces of the jigsaw will have to be in place by the end of July," when members plan to hold a new session.