Barack Obama has acknowledged that time has run out to secure a legally binding climate deal at the Copenhagen summit in December.
The President of the United States has also thrown his support behind plans to delay a formal pact until next year at the earliest.
During a meeting in Singapore this weekend, the US president supported a Danish plan to salvage something from next month's meeting by aiming to make it a first-stage series of commitments rather than an all-encompassing protocol as previously planned.
Postponing many decisions on emissions targets, financing and technology transfer until the second-stage, leaders will instead try to reach a political agreement in Copenhagen that sends a strong message of intent, writes The Observer.
Michael Froman, US deputy national security adviser for economic affairs, said: "There was a realistic assessment ... by the leaders that it was unrealistic to expect a full internationally legally binding agreement to be negotiated between now and when Copenhagen starts in 22 days," reports the newspaper.
Britain's climate change secretary Ed Miliband insists it is still possible to reach a broad political agreement on carbon emissions targets.
There is now expected to be intense discussions on whether the political agreement at Copenhagen contains any detailed commitments.