Although the White House did not give details of the closed-door talks, participants welcomed what they said was Obama's commitment to reduce greenhouse gases.

The president made "three things emphatically clear: We can make our economy stronger and our country more secure. We can put Americans back to work with clean energy jobs that can't be shipped overseas. And we can cut carbon pollution," said Natural Resources Defense Council (NRDC) president Frances Beinecke.

"These are vital objectives every American can get behind. This is about jobs. It's about national security. It's about the future of our country. And we will use every engine of persuasion at our disposal to help," Beineke said in a statement.

Beineke added: "We will work with the president to help pass clean energy and climate legislation. And we urge all Americans to support the president's mission to secure a strong international agreement at Copenhagen."

Meanwhile the head of the League of Conservation Voters, Gene Karpinski, said Obama "has reaffirmed his commitment to enact comprehensive clean energy and climate legislation next year.

"A comprehensive approach to energy -- including mandatory limits on carbon pollution -- will create the necessary market stability for entrepreneurs and businesses to invest in a new energy economy that will spark American ingenuity and create new clean energy jobs," he added.

Obama has been preparing this week for his visit to the Danish capital on December 18 to take part in negotiations at the global warming summit.

He kicked off on Monday by meeting former vice president Al Gore, who became a Nobel laureate for his efforts to raise awareness of climate change.

The US House of Representatives in June narrowly passed a plan to cut emissions by 17 percent by 2020 from 2005 levels.

Lawmakers in the Senate are still mulling their own climate bill, with Republican lawmakers remaining strongly critical of efforts to cut carbon emissions.

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