Barack Obama's transition team gave its clearest signal yet that the president-elect will act quickly to establish climate change as a top priority for his administration, prompting speculation that he could deliver significant changes to US environmental policy early next year.

Since his election victory Obama has repeatedly signalled that tackling the economic crisis will be his priority following his inauguration on 20 January next year, but yesterday one of his senior advisors hinted that economic measures are likely to go hand-in-hand with moves to deliver a new federal climate policy.

Speaking at a conference on carbon trading in Washington, Jason Grumet, the lead energy and environment adviser in the Obama campaign, said the president-elect will move quickly on climate change upon taking office.

"My suggestion to all of you is to enjoy the holiday season ... and rest up because I think it's going to be a very, very busy 2009," he told delegates at the conference hosted by Point Carbon and the Pew Centre on Global Climate Change.

Grumet - who is reportedly in the running for the post of energy secretary in the new administration alongside Senator Jeff Bingaman and Californian governor Arnold Schwarzenegger - offered no specific details about future policy, but hinted strongly that a significant tightening of environmental legislation is on the cards, observing that the US has "operated absent a federal climate policy, a federal climate program with mandatory elements, for many, many years now."

The comments are the latest in a series of hints from the Obama camp that the president-elect will make climate change and energy a central plank of his administration.

John Podesta, part of the troika overseeing the transition, said earlier this week that he anticipated Obama to move "very aggressively and very rapidly on the whole question of transforming the energy platform in the United States from high carbon energy to low carbon energy".

The Obama camp has also signalled that it will reverse any anti-environmental measures taken by president George W Bush during his last months in office, while proposals to link a bailout for the ailing US car industry to improvements in fuel efficiency were also reportedly near the top of the agenda when Obama met with Bush earlier this week.

The comments from Grumet sparked speculation Obama could move quickly to deliver a wide-ranging climate change bill, built around his pre-election proposals for a nationwide carbon cap-and-trade scheme.

However, some experts claimed that despite the Democrat's dominance of the government it will still take time for a climate change bill to become a reality.

Speaking at the Washington conference, Senator Jeff Bingaman, who chairs the Energy and Natural Resources Committee, said energy legislation would likely be passed ahead of new climate change rules.

"I wouldn't limit it to the first year (of the next two-year Congress)," he said of plans for cap-and-trade. "I think the reality is that it may take more than the first year to get it all done."

He added that passing energy legislation designed to better promote alternative sources of energy should come ahead of any carbon trading bill. "I think our prospects for moving ahead then and seriously considering and enacting cap-and-trade legislation is improved," he said.

Experts have also warned that it is likely to take several years to build a federal cap-and-trade scheme, noting that with widespread carbon auditing of the companies covered by such a scheme required before it can come into effect it is unlikely for a federal carbon market to be operational much ahead of 2011.