The G20 alliance of developing countries have unveiled an alternative plan to ease a deadlock in world farm trade talks which puts most of the onus on rich states in the sensitive area of tariff cuts.

The group, which is led by Brazil, India and South Africa, has rejected a joint EU-US blueprint on tariff barriers as being too soft on rich countries and too hard on the poor.

Its proposal, which will be on the table when negotiators meet in Geneva this week for farm negotiations, asks relatively little of developing countries, who would not have to open their markets to imports in products they decide are too sensitive.

"We consider this position a positive contribution to the negotiations," said Brazil's ambassador to the World Trade Organisation (WTO), Luiz Felipe Seixas Correa, who acted as spokesman for the group.

Reform of farm trade lies at the heart of WTO negotiations to lower barriers to business across the globe, the so-called Doha Round, and trade envoys are racing to complete outline accords before the summer break.

With the European Union signaling willingness to remove one potential obstacle to a farm deal by agreeing to discuss ending export subsidies, and with work well advanced on the question of the huge domestic subsidies rich states lavish on farmers, the main stumbling block has been import duties.

After rejecting the EU-US blueprint, the G20 offered to come up with an alternative before the next formal round of farm talks, which are scheduled to begin in Geneva on Wednesday. Allen Johnson, chief US agriculture negotiator, told reporters in Washington he was still reviewing the proposal. But at first blush, it appeared short on details, he said.