The United Nations conference on climate change in Montreal has agreed to hold long-term talks on measures to cut green house emissions.
Delegates at the conference, including the US, agreed to start new, open-ended talks that will seek co-operation to address climate change.
Meanwhile, countries taking part in negotiations on a successor to the Kyoto Protocol have agreed to start discussions to extend it beyond 2012.
The US, the world's largest emitter of greenhouse gases, pulled out of Kyoto in 2001, saying a fixation on emissions targets would harm economic growth.
Washington agreed to join the open-ended dialogue only after Canada and the EU watered down the text and spelled out that it would not lead to formal negotiations or commitments.
The US stance had been strongly criticised by the former US President, Bill Clinton, and the other participating countries had threatened to proceed without the United States.
Mr Clinton urged the US to back the deal on climate change.
Speaking in Montreal, Mr Clinton said the Bush Administration was utterly wrong in claiming that reducing green house gas emissions would hurt the US economy.
He added that it was time to look at the issue from a scientific point of view.
