INTERNATIONAL negotiators lost one of the key elements to a successful deal on global warming on Tuesday after Democratic leaders in the US Congress ruled out passing a climate change law before 2010. In the latest obstacle on the road to the UN summit in Copenhagen next month, Senate leaders ordered a five-week pause to review the costs of the legislation.

The delay, which would propel a Senate vote on a climate change bill into next year, frustrates a last-minute push by the German chancellor, Angela Merkel, and the UN secretary general, Ban Ki-moon, to get America to commit itself at home to cut emissions before the Copenhagen meeting. World leaders — and US officials — have repeatedly said US legislation is crucial to a deal on global warming.

Merkel used a historic address to a joint session of Congress on Tuesday to urge America to act on climate change, stating that success at Copenhagen rested on the willingness of all countries to accept binding reductions in carbon emissions.

The first German leader ever to address both houses of Congress, Merkel said a deal was comparable in importance to the tearing down of the Berlin wall 20 years ago. “We need the readiness of all countries to accept internationally binding obligations,” she said to loud applause from Democrats.

Republicans largely sat in silence. “There is no doubt about it. In December, the world will look to us the Europeans and the Americans. I am convinced once we ... show ourselves ready to adopt binding agreements we will also be able to persuade China and India.”

Merkel also raised her concerns with Barack Obama in a visit to the White House earlier in the day. He told reporters “Chancellor Merkel has been an extraordinary leader on the issue of climate change.

“And the US, Germany and countries around the world are all beginning to recognise why it is so important that we work in common to stem the potential catastrophe that could result if we see global warming continuing unabated.”

Ban is also pressing the US Senate to act before Copenhagen. Speaking in London, he said he would next week meet all the US senators involved in the deliberations over the energy and climate bill. Agreement on that bill is seen as vital without it, the US team in Copenhagen will have little domestic mandate to agree to a deal.

However, the appeals for urgent action were overridden by political concerns in the Senate, which formally began debate on a proposed climate change law last week. The House of Representatives narrowly passed a climate change bill in June. But the Senate version has been repeatedly delayed, first by the battle over healthcare reform and now by Republican demands for more time to study the proposals.

In a move to stem the Republican protest, and quieten Democrat critics, the Democratic leader in the Senate, Harry Reid, said he would ask the Environmental Protection Agency to spend five weeks reviewing the potential costs of the bill. Opponents of the proposal argue the target of a 20 per cent cut in emissions on 2005 levels by 2020 is overly ambitious, and will be too costly for US businesses and families.

The five-week delay would all but rule out passage of a bill before the Copenhagen meeting begins on Dec 7.

— The Guardian, London