LONDON - Ministers from key trade powers begin last ditch talks on Monday that could save or sink floundering negotiations on a global deal aimed at energising economies and lifting millions out of poverty.

With the clock racing towards a mid-December deadline, ministers from the United States, the European Union, Japan, Brazil and India are due to meet at the Indian embassy in London to try to bridge differences before the venue switches to Geneva on Tuesday and more ministers join.

After some four years of negotiations, the gap between rich and poorer countries, particularly over agriculture, remains dauntingly wide and unless a way can be found to narrow it fast, all sides have warned the negotiations face collapse.

"It is a pretty serious situation and people have just got to face up to it," said a top envoy from a leading developing country.

World Trade Organisation (WTO) Director-General Pascal Lamy, who will be at all the talks, warned that failure would cost the world economy hundreds of billions of dollars in lost trade opportunities and that poorer countries would lose the most.

With agriculture still the thorniest issue, the EU will be under heavy pressure to bring down barriers to imports after its latest offer was spurned as inadequate by major partners.

However, EU Trade Commissioner Peter Mandelson is also being harried by European countries such as France, the largest beneficiary of EU farm support, which has warned it would veto any deal that gave too much away on agriculture.

The EU insists it has gone as far as it can on agriculture, the area where developing countries feel they have most to gain from liberalisation, and that it is time to focus on industrial goods and services - two other pillars of the WTO's Doha Round.

Leading developing nations such as Brazil and India, which head the influential G20 poorer nation alliance, say they are still not ready to make concessions elsewhere until they are satisfied with the farm package.

Brazil, echoed by other farm goods exporters such as Australia, reject what the EU has put on the table saying it would exclude most of the products they are really interested in - such as beef, poultry and sugar - from deep tariff cuts.

The United States, although it has made concessions on farm subsidies, is being asked for more because developing states, notably India, say it can still dump products on world markets.

If no breakthrough comes in the London or Geneva talks, diplomats say the WTO will face difficult choices over what to do about the Hong Kong ministerial meeting starting on December 13 when the detailed blueprint for the round is due to be approved.

They could opt to lower the bar for Hong Kong, but for that there must be an understanding that a deal would be struck quickly afterwards, diplomats say.

Alternatively, they could lower the targets for the round itself and try and stitch together a trade treaty based on the little that has so far been agreed - but that risks satisfying nobody, they add.