The daylong discussions mark yet another attempt to resolve differences and draft a treaty in time for the WTO's conference in Hong Kong, now just two months away.

Much of the meeting is expected to focus on disagreements between the United States and European Union over concessions on customs duties and government aid to farmers.

It is also likely to consider how to satisfy the demands of developing countries, which are pressing rich nations to do more to open their markets to farm goods.

Freeing up the farm trade has proven a key stumbling block in talks among the 148 trading nations in the WTO -- although talks on industrial goods and services, such as insurance and banking, are likewise far from a breakthrough.

Ahead of the meeting the US' top trade official said Washington was proposing to slash its agricultural subsidies by 60 percent by 2010, in what he called a bid to jumpstart the negotiations.

"To jump-start our stalled negotiations, the US is prepared to move, and move aggressively, by supporting a 60 per cent cut in "amber box" support -- the most distorting type of subsidies -- over the next five years," US trade representative Rob Portman said in the online edition of the Financial Times.

"This will require significant reforms to US farm programmes."

But in a sign of the horsetrading ahead he said greater cuts must be required by the European Union and Japan, which he said have much larger agricultural subsidies.

"All countries must also simultaneously deliver real market access," he pointed out.

Besides the United States and European Union, the other countries expected in Zurich are a cross section of the WTO's membership: Australia, Brazil, Canada, China, Egypt, Hong Kong, India, Japan, Kenya, Malaysia, Mexico, Rwanda, South Africa, South Korea and Switzerland.

Last week, a senior US government official said the aim would be to "talk candidly."

The WTO's members set the rules for international trade.