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WASHINGTON, Jan 26 (Reuters) - Secretary of State Hillary Clinton named a special envoy on Monday to lead U.S. efforts to fight global warming and forge new international accords on reducing carbon emissions and developing clean energy.

The appointment -- which accompanied other energy policy steps announced by President Barack Obama -- signaled a break from the Bush administration's climate policies, and Clinton's pick promised "vigorous, dramatic diplomacy."

Todd Stern, a senior White House official under former President Bill Clinton, will be the administration's principal adviser on international climate policy and strategy and its chief climate negotiator.

"With the appointment today of a special envoy we are sending an unequivocal message that the United States will be energetic, focused, strategic and serious about addressing global climate change and the corollary issue of clean energy," Clinton said at a State Department ceremony.

Stern's appointment came as Obama announced moves to force auto makers to produce more fuel-efficient and less polluting cars, including telling the Environmental Protection Agency to reconsider a California request to impose strict limits on vehicle carbon dioxide emissions. [ID:nN26491768]

"As we take steps at home, we will also vigorously pursue negotiations, those sponsored by the United Nations and those at the sub-global, regional and bilateral level, that can lead to binding international climate agreements," Clinton said.

"No solution is feasible without all major emitting nations joining together and playing an important part," she said.

Stern coordinated climate change policy from 1997 to 1999 in her husband Bill Clinton's administration, acting as the senior White House negotiator in the Kyoto talks.

About 190 countries are trying to craft a broader climate treaty to replace the Kyoto Protocol that binds wealthy nations to emission targets between 2008 and 2012. The new deal is supposed to be wrapped up in Copenhagen by December.

"The time for denial, delay and dispute is over. The time for the United States to take up its rightful place at the negotiating table is here," Stern said.

"We can only meet the climate challenge with a response that is genuinely global," he said. "We will need to engage in vigorous, dramatic diplomacy."

From 1999 to 2001, Stern advised the U.S. Treasury secretary on economic and financial issues and supervised the department's anti-money laundering strategy. He is a partner in a Washington law firm and a senior fellow at Center for American Progress think tank, which is home to many veterans of the Clinton administration. (Additional reporting by Sue Pleming and Arshad Mohammed; Editing by Frances Kerry)