The US Senate will complete the framework of climate change legislation before next month's high-stakes summit in Copenhagen, Senator John Kerry promised UN chief Ban Ki-moon on Tuesday.

"We are engaged in the process that will hopefully put us in a position to go to Copenhagen with a sort of framework, or outline, or where the Senate will be heading in its legislation," Kerry told reporters after meeting Ban at the US Capitol.

The Senate has not followed the House of Representatives in finalizing the first-ever US federal caps on carbon emissions, raising fears that the December 7-18 talks in the Danish capital will flop without the world's biggest economy.

Kerry, a former presidential candidate who authored climate change legislation introduced into the Senate, said he told Ban that senators were "engaged in a very intensive process.

"What I wanted to convey to the secretary-general -- and I think it's important to all those taking part in Copenhagen -- is we are very serious about our goal," Kerry said.

Ban, who has made the fight against climate change one of his top priorities, said he was encouraged by his day-long trip to Washington, calling a Senate framework a "sign of commitment" to the rest of the world.

"I have emphasized to the senators that US leadership is crucial at this time," Ban told the joint news conference with Kerry and other senators.

"No country is more important than the United States in resolving this climate change issue. All eyes of the world are looking to the United States and more precisely to the US Senate," he said.

Climate change legislation squeaked through the full House in June and last week members of Obama's Democratic Party rammed legislation through the Senate's key Environment and Public Works Committee, with Republicans boycotting.

But other committees are still working on the bill, meaning it cannot come to a full Senate vote. Senator Max Baucus, a centrist Democrat who heads the Finance Committee, has pushed for more guarantees the legislation will not worsen the wobbly US economy.

Kerry, however, said he understood that Baucus has not made a "final decision" on climate legislation.

Kerry did not specify the exact form that the Copenhagen framework would take but said he would be careful not to pre-empt committee work by Baucus on the financing of climate legislation.