US President-elect Barack Obama has pledged to "engage vigorously" on climate change, ahead of next month's UN summit on the issue.

Mr Obama will not be at the talks in Poland but said the US would "help lead the world" once he has taken office. His comments came in a video message to a gathering of US state governors.

Next month's summit is a staging post in a two-year process aimed at securing a new climate treaty when current Kyoto Protocol targets expire in 2012.

Mr Obama will not be attending the UN Framework Convention on Climate Change (UNFCCC) talks, he explained, because "the United States has only one president at a time".

But, he continued: "Once I take office, you can be sure that the United States will once again engage vigorously in these negotiations, and help lead the world toward a new era of global co-operation on climate change."