U.S. Wins Concession on Emissions : Global warming: The proposal backs off from a cap on greenhouse gases. Critics call it a sellout.

In what could be a turning point in protracted talks over a global warming treaty, key negotiators agreed Friday to a U.S. demand that there be no firm deadline for reducing greenhouse gases.

The proposal, if ultimately approved, would represent a major retreat from European insistence that emissions of greenhouse gases be stabilized at 1990 levels by the year 2000.

Instead, the latest proposal merely calls for a return to “earlier” emission levels by the year 2000. Critics said that vague wording could mean a return to the higher levels expected in 1999.

Drafted behind the scenes by U.S. and British negotiators, the proposal was introduced by the French chairman of the U.N. negotiating session, Jean Ripert. It drew immediate criticism from developing countries as well as environmentalists, who characterized it as a “sellout.”

Ripert emphasized that the draft is subject to change as negotiations continue through next week. Nonetheless, some environmentalists worried that the final treaty text expected to emerge by the end of the week could closely follow Friday’s proposal.

“The chances are this text will survive,” said T. J. Glauthier, director of energy and climate-change policy for the World Wildlife Fund and the Conservation Foundation. “It was approved at the highest levels of government. They’ll work very hard to keep from changing it.”

Officially, the United States was describing the proposal as Ripert’s and said Washington was “encouraged” by the development. In large part, the text is Ripert’s, but a vital section deleting the firm deadline for stabilizing emissions of carbon dioxide--a key greenhouse gas--was reportedly drafted by high-level U.S. and British negotiators.

Indeed, Ripert told reporters, “I consider this is a very important move of the government of the U.S. even though it is not my language.” Asked if there was a binding emission-reduction target in the text, Ripert said simply, “You will not find this language in my paper because no government is in a position to guarantee levels of emissions.”

Governments, he added, have no control over the weather or how robust their economies might be.

But he said the language represented a starting point to address mounting international concerns about global warming.

“We need to start somewhere,” he said. “We are dealing with a very difficult question. You don’t decide that in one day French citizens and American citizens are going to change their lifestyles.”

In Washington, an Administration source said the United States and some European countries were nearing agreement on the approach. The real problem, the source said, is that while the United States and other industrialized nations could meet or come close to stabilizing emissions by the year 2000, reductions after that time could be difficult.

Environmentalists assailed the proposal. Rafe Pomerance of the World Resources Institute, a private environmental policy group based in Washington, held out hope that the wording could be strengthened before the scheduled end of negotiations next week.

Greenhouse gases threaten to raise the Earth’s temperatures by trapping the sun’s heat in the atmosphere. A chief source of carbon dioxide comes from the burning of fossil fuels such as coal, oil and gasoline.

Times staff writer Rudy Abramson in Washington contributed to this report.