US President Obama is pledging a provisional target for reductions in greenhouse gas emissions in the US, the first time an American administration offered even a tentative promise to reduce production of climate-altering gases, White House officials said on Wednesday. Obama will travel to the UN climate change conference in Copenhagen next month to deliver the pledge in hopes of spurring significant progress at the talks.

Obama will tell the delegates to the climate conference that the US intends to reduce its greenhouse gas emissions “in the range of” 17 per cent below 2005 levels by 2020 and 83 per cent by 2050, officials said. No American administration has ever delivered even a tentative pledge on emissions reductions because Congress has never enacted climate legislation or approved an international global warming agreement with binding emissions targets.

Obama, who had not previously committed to making an appearance at the climate summit, had been under considerable pressure from other world leaders and environmental advocates to make the trip as a statement of American seriousness about the climate change negotiations. He will appear on December 9, near the beginning of the 12-day session, on his way to accept the Nobel Peace Prize in Oslo on December 10, officials said.

By making the pledge in an international forum, Obama is laying a bet that Congress will complete action on a bill next year and will be prepared to ratify an international agreement based on the commitment.