The epic battle over universal health care is still to be fought, but Barack Obama moved to capitalise on a defining moment of his presidency yesterday - a vote in Congress to act on global warming - saying the time had arrived for America to show international leadership on climate change.

The White House shifted the topic of Obama's address from healthcare to energy after the vote, seeking to build momentum for the ambitious climate change bill ahead of its next hurdle in the Senate. The first round, in the house of representatives on Friday night, barely went to Obama. The Democratic leadership, despite making concessions to dissidents from oil and coal states, eked out only a 219-212 victory. A total of 44 Democrats opposed the bill.

But environmentalists claimed the vote as a milestone: the first time either house of Congress had acted to reduce the carbon emissions that cause climate change. It was also a validation of Obama's powers of persuasion. The president put energy reform at the heart of his White House agenda and jumped into a furious lobbying effort for its passage.

In his video address, Obama sought to bring home Friday night's victory, calling on the Senate to approve the bill so that America could catch up to the rest of the world in moving to a cleaner energy economy.

"We have seen other countries realise a critical truth: the nation that leads in the creation of a clean energy economy will be the nation that leads the 21st-century global economy," he said. "Now is the time for us to lead."

The international community had been waiting for America to take action on climate change and the vote gave a boost to efforts to reach a deal to avoid the most catastrophic effects of climate change.

India, a key player in the negotiations to reach a deal at Copenhagen, gave a cautious welcome. "Obviously having the US take the lead on climate change would have a significant impact on the current multilateral negotiations," India's climate change envoy said. "We would hope that the US will lead with ambitious actions."

Environmentalists, who had despaired during eight years of George Bush of ever seeing action on climate change, said the bill, though weaker than they might have liked, was still a signature achievement.

"The fact is, just weeks ago, few in Washington believed that this day would come to pass. The best bet - the safe bet - was that after three decades of failure, we couldn't muster the political will to tackle the energy challenge despite the necessity and urgency of action," Obama said on Friday night.

The bill would gradually impose a ceiling on the carbon emissions that cause global warming, ultimately cutting them by 83% from 2005 levels by 2050 by forcing industries to obtain permits for the emissions they release in the atmosphere, or to buy offsets by investing in cleansing projects like planting trees.

The bill would also compel utility companies to obtain a share of their electricity from renewable sources such as wind and solar.

The biggest weakness in the bill is its target of cutting carbon emissions by 17% from 2005 levels by 2020, which represents only a marginal reduction compared with Europe.

However, Greenpeace opposed the package, saying it had been badly weakened by the concessions made to win over conservative Democrats from oil and coal states.