The US may be willing to back an agreement at next month's G8 summit on cutting carbon dioxide emissions, Tony Blair has said on BBC TV.
Germany has made climate a priority for the G8 presidency
Up to now, the Bush administration has championed voluntary agreements as an alternative to imposing binding caps.
Germany has made climate change a priority for its G8 presidency.
The prime minister said awareness of the issue among Americans was growing and it was possible the US will sign up to "at least the beginnings" of action.
Last September, California became the first US state to set targets to reduce greenhouse gas emissions.
Speaking on the BBC's Newsnight programme, Mr Blair was asked how he was going to persuade President George W Bush to agree to national impose limits on CO2.
"You've got several of the states now doing it," Mr Blair said.
"I can't think that there's going to be many people running for presidential office next time round in the US who aren't going to have climate change in their programme."
He added: "I think it is possible that we will see action - and at least the beginnings of that action at the G8 - I hope so. That's what I'm arguing for."
Mr Blair's comments on Newsnight came after the G8 countries, together with China, India, Mexico, Brazil and South Africa, have been holding talks on emissions.
"For the first time, at least the Americans are in this G8 plus 5 process," Mr Blair said.
But only last week a UN-hosted meeting ended with the US indicating it was unlikely to take part in negotiations at the end of this year on a global agreement to cut emissions.
And according to documents seen by the BBC, the US is trying to block sections of a draft agreement on climate change prepared for the G8 summit.
Washington is said to object to the targets to keep the global temperature rise below 2C this century and halve greenhouse gas emissions by 2050.