There is growing evidence that President Obama will be forced to delay signing up to any new agreement on climate change in Copenhagen due to the scale of opposition in the US Congress.

Senior figures in Obama’s administration have warned their political counterparts in London that Obama may need another six months to win domestic support for any proposal. Analysts believe such a delay could scupper any deal at Copenhagen.

American officials would prefer to have the approval of Congress for any international agreement and fear that if the US signed up without it there would be a serious domestic backlash.

The White House’s new chief science adviser, John Holden, was a member of the climate change taskforce and Todd Stern, one of its advisers, is working with Hillary Clinton at the State Department and will lead negotiations for the US in Copenhagen.

Hilary Clinton’s special envoy on Climate Change, Todd Stern, has warned it will be a tall order to get congressional approval before Copenhagen. Stern’s preference would be for the US go to Copenhagen with that crucial approval:

He argues: “The optimum would be [climate] legislation that is signed, sealed and delivered. It has been a long time now that countries have been looking for the United States to lead and take action. I think nothing would give a more powerful signal to other countries in the world than to see a significant, major, mandatory American plan.”

But the opposition within America is potentially substantial with as many as 15 Democratic senators who represent “rust-belt” states dependent on coal mining, steel production and heavy manufacturing, all big emitters of carbon, who could all vote against any deal.

There may have been a political paradigm shift in Washington but old carbon habits die hard.