History suggests that talk of "do-or-die" surrounding the meeting of trade ministers that starts today in Geneva deserves to be greeted with weary cynicism.

Ever since the collapse of the World Trade Organisation's ministerial conference in Cancún, Mexico, in 2003, the WTO's 152 members have been trying to agree a framework deal in the Doha round of global trade talks.

On each occasion, ministers warn that failure risks sinking the round. Yet the negotiations have resumed. Still, there are good reasons for believing that this really is, in the words of Pascal Lamy, the WTO directorgeneral, the "moment of truth" for the seven-year-old round, launched in Qatar's capital in 2001.

The looming US presidential poll in November rules out serious negotiations after the WTO's August break. Concluding a global trade pact is unlikely to be high on the priority list of a new US administration, Democrat or Republican, faced with rising protectionist sentiment.

Nor is next year's political calendar favourable to trade talks, with changes in the executive of the European Commission and a general election in India - a key participant in the round.

Mr Lamy says that "freezing" what is currently on the Doha table, and picking up again in a year or two, is simply not an option. He is not alone in believing that if a deal is not done now, the round will be abandoned as future trade talks respond to a changed global agenda. A lot is on the table already, including agreement in principle to big cuts in rich-country farm subsidies that hurt producers in poor nations, and lower tariffs on agricultural and industrial goods. Also in the works are prospective deals on liberalising trade in services, easing customs procedures, disciplining fishing subsidies and revising anti-dumping and intellectual property rules.

Peter Mandelson, EU trade commissioner, pointed out last week that failure in Geneva could hit multilateral accords on climate, food prices and energy security.

But it is by no means certain that ministers will conclude the required framework agreement this week on lowering trade barriers to agricultural and industrial goods. Some are optimistic, but Mr Lamy puts the odds of success below his "comfort zone" of 70-80 per cent.

This time the key stumbling blocks may not be the "headline" numbers on farm trade. Both the US (on subsidies) and the EU (on tariffs) indicate they can move if they get extra market access in fast-growing emerging economies for their own goods and services.

But rich and poor nations are far apart on how much developing states should cut industrial tariffs, and big differences remain on the amount of discretion developing countries will have to maintain high protective barriers on certain farm and industrial goods.

Even before the talks began, key negotiators were seeking to blame others for any breakdown. Susan Schwab, US trade representative, said advanced developing nations needed to make "meaningful market opening contributions".

EU member states also called for more market access from emerging nations. But Celso Amorim, Brazil's foreign minister, said later that rich countries were not doing enough on agriculture while making unreasonable demands in industrial goods - calling this "a recipe for failure".

There are also unresolved disputes over cotton and bananas. The WTO works by consensus, so a single veto could bring the whole Doha edifice crashing down.

Deal would aid European farmers, Page 13