But diplomats from developing countries, which are particularly suspicious of what they see as a bid to introduce "green protectionism," said the plan remained unacceptable.

"We are not prepared to open any negotiations on this issue," said one South American diplomat.

The developing countries, backed by the United States and other rich states, believe existing WTO accords fully cover all legitimate environmnental concerns.

"The U.S. did not see a case for opening rules for negotiation," a senior trade official, who attended Monday's meeting, told journalists.

The 142-member WTO is seeking agreement on draft texts for a declaration to be issued by the ministers at the November 9-13 meeting in Doha, Qatar, as well as a deal on how to handle the developing countries' complaints.

WTO director-general Mike Moore has been leading the campaign for a new trade round which he sees as vital to give a shot in the arm to the ailing world economy.

Many developing countries, however, say that the WTO needs to address perceived shortcomings in existing free trade accords before launching a new round.

But diplomats say the starkest differences now on display are over the environmental issue - labelled by the EU at a meeting last week of the WTO's ruling General Council as "of prime political importance" to Brussels.

"The resistance faced by the EU all along remains," said one trade official.