WTO ministers failed to reach breakthrough in the Doha Round trade opening talks after nine days of wrangling in Geneva, trade sources said Tuesday.

Intensive negotiations among the WTO's seven key members broke up mainly due to sharp differences on agricultural SSM (special safeguard mechanism) for developing countries and cotton subsidies by the United States, the sources said.

The seven key members include the United States, European Union, Australia, Japan, Brazil, India and China.

The SSM is a mechanism which allows developing countries to raise farm tariffs if imports surge, thus protecting the interests of poor farmers.

Sources close to the negotiations said that six members of the G7 had reached consensus on the SSM issue, except the United States.

In the G7 meeting, U.S. Trade Representative Susan Schwab also refused to talk about cutting of huge U.S. cotton subsidies, which is a major concern for poor cotton farmers in African countries.

WTO chief Pascal Lamy has informed a wider meeting of some 30 ministers that convergence could not be reached after nine days of talks.

He will later announce the failure at a meeting of WTO heads of delegations.

Trade and agricultural ministers from 35 major WTO members have been meeting in Geneva since July 21, trying to reach an outline agreement on agriculture and NAMA (non-agricultural market access),the two key areas of the Doha Round.

But the negotiations have been tough from the beginning and they had been on the verge of failure for several times.

The Doha Round had been troubled by issues of agriculture and NAMA since it was launched in 2001, and it had missed repeated deadlines for conclusion.

Editor: Yan