"President Barack Obama should work it out with the Senate, how to come to Copenhagen and bind the US," EU environment commissioner Stavros Dimas told an environment conference in Athens.

"It is a matter of political will. We await, and I am certain President Obama will honour his pledge on climate change," he said.

Some 190 countries will meet in Copenhagen between December 7-18 to try to conclude a new UN-backed climate treaty to replace the Kyoto Protocol, which expires in 2012.

The US Senate is debating a bill calling for a 20-percent cut in greenhouse gas emissions by 2020, but Republican Senators opposing the measure are mostly shunning the procedure.

Senate Democrats on Thursday pushed the bill through one key committee but five other committees have jurisdiction over the legislation and identical versions must clear the Senate and House of Representatives.

Democrats have mostly abandoned hopes of wrapping up the process before the Copenhagen talks, a fact acknowledged by Dimas who said a Senate vote "seems less likely now."

But he noted Washington's drastic change of policy since Obama replaced George W Bush as the US president in January.

"During the barren Bush years, you could not talk to the Americans on climate change," said Dimas, who has held the post for five years.

"They didn't even want to hear the word 'Kyoto'. It was not part of their vocabulary, it was like talking to a wall. This position has now been overturned."

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