PRAGUE ? United States President Barack Obama promised on Sunday to take the lead in global efforts to tackle climate change, which Europe has long accused Washington of failing to address seriously.

"To protect our planet, now is the time to change the way that we use energy," he told a crowd gathered at Prague Castle for his only public speech during his maiden tour of Europe.

"Together we must confront climate change by ending the world's dependency on fossil fuels by tapping the power from the sources of energy like the wind and the sun and calling upon all nations to do their part," he said.

"And I pledge to you that in this global effort the US is now ready to lead."

Obama was speaking ahead of the new president's first EU-US summit, with European leaders eager for signs that Washington is willing to play a new role in cutting greenhouse gas emissions.

Under the leadership of George W. Bush, European leaders were often exasperated by the US failure to commit itself to climate change targets, especially because Europe has set ambitious targets for cutting greenhouse gases.

Swedish Prime Minister Fredrik Reinfeldt and Spanish counterpart Jose Luis Rodriguez Zapatero, whose countries are next in line to assume the EU presidency, are set to head the debate on climate change, according to diplomats.