Representatives of 22 nations held two days of informal talks in Tokyo this week to pave the way for a December meeting in Copenhagen which is supposed to approve a new post-Kyoto international climate treaty.

"I assure you that there is a sea change in the tone of the new US administration," Artur Runge-Metzger, the top EU negotiator on climate change, told reporters.

He said the Tokyo meeting was his first contact with US climate officials since Obama's inauguration last month, although no new political appointees attended the talks.

"There is a willingness to engage on the issue of climate change and to show leadership and the best sign was that many of the senior positions on climate change have already been filled in the Obama administration," Runge-Metzger said.

The Obama administration has appointed as its climate negotiator Todd Stern, a veteran of the talks that led to the landmark Kyoto Protocol which for the first time required nations to cut carbon emissions blamed for global warming.

Former US president George W. Bush snubbed the Kyoto treaty in 2001 as one of his first acts in office, saying it was too costly for the world's largest economy.

Obama has also made a sharp change of gear by signing measures to encourage production of fuel-efficient cars and vowing US leadership in the fight against global warming.

The Copenhagen meeting is meant to set commitments for the period after 2012, when Kyoto's obligations expire.

Under Bush, the United States resisted calls to fix more binding targets for emission reductions.

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