BEIJING/COPENHAGEN, (Reuters) – U.S. President  Barack Obama said yesterday next month’s climate talks in  Copenhagen should cut a deal with “immediate operational  effect,” even if its original aim of a legally binding pact is  not achievable.

About 40 environment ministers meeting in Copenhagen made  progress towards a scaled-down U.N. deal next month, while  African leaders accepted for the first time that the December  meeting would not agree a full treaty.

Obama was speaking after talks with Chinese President Hu  Jintao in which he said the world’s top two greenhouse gas  emitters had agreed to take “significant” action to mitigate  their output of carbon dioxide. The two countries account for more than 40 percent of  global carbon emissions from burning fossil fuels.

“Our aim (in Copenhagen) … is not a partial accord or a  political declaration but rather an accord that covers all of  the issues in the negotiations and one that has immediate operational effect,” Obama said.

But a senior U.S. senator, Obama’s fellow Democrat Barbara  Boxer, yesterday predicted that Washington officials will  arrive at the Copenhagen summit without consensus on how deeply  the United States can promise to cut its own carbon emissions  by 2020.

Boxer, who chairs a Senate environment panel that recently  approved a climate change bill that lacks enough support to  pass the full Senate, left open the possibility that U.S.  negotiators instead might offer a range for U.S. carbon  reductions by 2020.

Denmark, host of the Dec. 7-18 climate talks, won backing  from Obama and other leaders at an Asia-Pacific summit on Sunday for Danish Prime Minister Lars Lokke Rasmussen’s  scaled-down plan for a politically binding deal in December,  and a legally binding one in 2010.

Rasmussen yesterday welcomed Obama’s comments and said it  expected the United States and all developed nations to promise  firm emissions cuts and new cash to help the poor cope with  global warming, even if no treaty text could be agreed.

At the final preparatory meeting before the Copenhagen  summit, environment ministers in the Danish capital put  pressure on Washington to do more to unlock talks.

“My feeling is that it looks better today than when we  started meeting,” Danish Climate and Energy Minister Connie  Hedegaard told a news conference after two-day talks.

“In the end, an agreement in Copenhagen will depend on an  American number. Without a clear and ambitious number the whole  agreement will be in danger,” Swedish Environment Minister  Anders Carlgren told Reuters.

Obama’s call yesterday for a broad agreement taking effect  immediately suggests he is keen to walk away from the climate  summit with more than just a piece of paper. But the stalling  of legislation hampers him.

Washington has been reluctant to promise firm emissions  cuts by 2020 without domestic carbon-capping legislation which  Democrat supporters hoped the Senate would approve next  spring.

Andrew Light, a senior fellow at the Center for American  Progress in Washington, told Reuters U.S. officials had  recently raised expectations that the United States “will put  down a number” in Copenhagen for carbon goals, to become part  of a final deal.