The United States will take a carbon emissions reduction target to the UN climate conference in Denmark in two weeks’ time.
Many countries including big carbon emitters China and India have been waiting to see Washington’s position before putting forward their own.
The actual figure will be announced in the next few days according to a White House official who spoke on condition of anonymity. But the reduction is expected to be in line with proposals in the US Senate – a cut of between 17 and 20 per cent on 2005 levels.
It is also expected to be announced this week whether Barack Obama will join at least 65 other heads of state and government in Copenhagen.
They are being urged by environment groups to put numbers on the table and set clear global targets.