By Richard Black
Environment correspondent, BBC News website
Some Republicans wanted to expand oil drilling to meet US energy needs
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."
The decision by White House incumbent George W Bush in 2001 to withdraw from the Kyoto Protocol is widely seen as the principal reason why the treaty came into force later than planned and with a much weaker impact on greenhouse gas emissions than its architects had envisaged.
Earlier this week the UNFCCC reported that greenhouse gas emissions from developed nations rose by 2.3% between 2000 and 2006.
Mr Obama's video message was played at the opening of the Governors' Global Climate Summit, a session called and hosted by California's Governor Arnold Schwarzenegger.
On the eve of the meeting, Mr Schwarzenegger announced plans to have his state generate one-third of its electricity by 2020 from renewable sources.
Climate and energy security are interlinked issues for the US
If replicated nationwide, that would take the US some way towards the national target Mr Obama espoused during his election campaign, of reducing greenhouse gas emissions by 80% by 2050.
Alongside his pledge to re-engage with the UN process, the president-elect also promised during his campaign to establish "a Global Energy Forum of the world's largest emitters".
The parallel fora established under Mr Bush's presidency - the Asia-Pacific Partnership on Clean Development and Climate and the Major Economies (or Big Emitters) group - were seen as diversions from the UN process, and it is not yet clear how Mr Obama sees the relationship between the UNFCCC and his proposed new body.
Although he will not be at the UN summit next month in Poznan, the president-elect said he would ask members of Congress to "report back".
Outside the US, his leadership is widely seen as crucial to achieving a significant treaty. But timescales are clearly an issue.
The "roadmap" leading from last year's UN summit in Bali is supposed to conclude with the signing of a new global treaty at the end of 2009.
As Mr Obama's team may not be in place for several months, and would then have to agree a joint US position with Congress, the 2009 target looks difficult.
The EU has floated the possibility of holding an interim UN summit, perhaps in the middle of next year, at which the Obama presidency could play a full role.