Marathon talks to salvage a global trade pact collapsed on Tuesday as the United States and India refused to compromise over a proposal to help poor farmers deal with floods of imports.

The World Trade Organisation (WTO) Director-General Pascal Lamy announced the failure of the ministerial meeting seeking a breakthrough of the Doha Round had collapsed.

The ministers were "simply not able to bridge their differences ", Lamy told a press conference after the breakup of negotiations by trade ministers from some 35 major WTO members.

He said the negotiations failed mainly due to sharp differences on agricultural SSM (special safeguard mechanism) for developing countries and cotton subsidies by the United States.

Chinese Commerce Minister Chen Deming expressed his regret that the talks had broken down over differences between two countries -- a reference to the United States and India -- over a proposal to help poor farmers cope with import surges, despite flexibility by China on a range of trade areas, according to a statement.

The "tragic failure" is a serious setback to the troubled world economy, Chen said.

"In the face of a world economic downturn, serious inflation and imminent financial risks, the failure will have a major impact on the fragile multilateral trading system," Chen told fellow ministers at the trade talks.