The Bush administration is warming to the idea of reducing carbon emissions, Tony Blair has claimed.
Speaking after the launch of his government's much-anticipated energy review, the prime minister said the US was beginning to take action that could benefit the global environment.
President Bush has drawn criticism from environmental campaigners because of his failure to back the Kyoto Protocol.
But according to Mr Blair, other countries "hide behind America" when it comes to combating climate change, adding that most European countries are failing to meet their Kyoto targets.
In an interview with the BBC's Newsnight last night the PM said there had been some encouraging signals from his closest political ally.
"President Bush's speech - the state of the union address - that America should move to a low carbon economy, is an important indication that, albeit for reasons of energy security rather than necessarily being driven by climate change, there is going to be change happening there," he said.
Mr Blair added that it was vital for the international community to work with the US, which is the world's biggest polluter, as well as the fastest growing economies, China and India, to secure long-term agreements.
"The truth is, as the Chinese economy grows and grows and will, eventually, become the largest economy in the world with India not far behind, then there is no alternative but to make sure you have an agreement that involves all the main CO2 emitters," the prime minister noted.
Yesterday's energy review sought to address the UK's own climate change targets, as well as the issue of securing future supplies.
The government has said that it wants energy efficiency and renewables to take centre stage but has left open the option of building more nuclear power stations, despite opposition from green campaigners and some Labour MPs.