Oct. 30 (Bloomberg) -- A treaty to curb global warming probably won’t be completed in Copenhagen in December, and countries should ratchet down hopes for such an accord, a former U.S. climate-change negotiator said.

“I do wish some government would actually start to lower expectations rather than keep raising them,” Eileen Claussen, a former State department official under President Bill Clinton, told reporters today in Washington.

The most likely scenario when more than 192 nations gather in Denmark in December is a political agreement with a new deadline to reach an accord on a treaty to replace the existing Kyoto Protocol, which expires in 2012, said Claussen, head of the Pew Center on Global Climate Change in Arlington, Virginia.

Carol Browner, the White House coordinator for energy and environment, said this week that the administration is “very confident” that it can help forge progress in the treaty discussions.

The view that longtime differences between industrialized and developing countries could be resolved in time to complete an accord at the United Nations-led negotiations in Copenhagen stems in part from optimism that President Barack Obama would be able to deliver a clear U.S. negotiating position this year, according to Claussen.

“Some of this has to do with the very high expectations I think of the Obama election and the sense, unrealistic sense, that that could turn everything on its head in a really fast time frame,” she said. “We just don’t move that fast on big issues.”

Possible Savior

When Obama was elected president, he was heralded as a possible savior for climate-treaty talks that had dragged on for years while President George W. Bush rejected limits on U.S. greenhouse-gas emissions.

Instead, the U.S. envoys may be empty-handed because Congress has given Obama no mandate. The U.S. may be blamed by other countries for lack of progress in Denmark, Elliot Diringer, Pew’s vice president for international strategies, said today.

“The worst case would be something that’s widely perceived as a failure and a failure that is blamed entirely on the United States,” he said.

The Obama administration also hasn’t given up on getting a climate bill through the Senate this year, and can point to actions aimed at cutting greenhouse gases, such as proposed tailpipe emissions standards and investments in clean energy, Browner said in an Oct. 27 interview.

“We feel very, very confident that we can work with the rest of the world to take significant steps forward in Copenhagen,” she said.

To contact the reporter on this story: Kim Chipman in Washington at kchipman@bloomberg.net.

Last Updated: October 30, 2009 12:49 EDT