WASHINGTON - President Barack Obama is unlikely to sign climate legislation ahead of a December U.N. global warming meeting in Copenhagen, the White House's top climate and energy coordinator Carol Browner said on Friday.

We'd like to be (finished with) the process. That's not going to happen, Browner said at a conference called the First Draft of History.

Democratic Senators John Kerry and Barbara Boxer unveiled a climate bill this week but it is unclear whether it would win the required 60 Senate votes for passage.

Even if it does pass the U.S. Senate, it would still have to go to committee between the Senate and the U.S. House of Representatives, which would leave little time for Obama to sign the bill.

Browner said the Administration was pleased with talks it has had with China, the world's top greenhouse gas polluter, on tackling climate change.

If the bill fails in the Congress in due time, the Administration has options, she said. The U.S. Environmental Protection Agency could work with states that already have formed carbon markets to extend those programs, said Browner, who used to head the agency.

That may be a way in which you could form a regime using these models that are already out there, Browner said.

Ten states in the U.S. East have formed a program known as the Regional Greenhouse Gas Initiative that regulates carbon dioxide emissions from power plants.

(Reporting by Timothy Gardner; Editing by Marguerita Choy)