A deal to tackle global warming was salvaged after Britain made a direct appeal to Washington, it has emerged. US delegates had walked out of the UN climate change conference in Montreal. But they later returned and agreed to sign up to non-binding talks on long-term measures to tackle global warming.

It appears the move came after the British Government made a call to the White House. Environment Secretary Margaret Beckett said there were "conversations to and fro between London and Washington".

But she would not say if the Prime Minister had spoken directly to President Bush. Downing Street also declined to say. Mrs Beckett said just an hour before the deal was struck on Saturday it appeared the talks were going to end in failure. Speaking on the BBC's Sunday AM programme, she said the Americans were nervous about the text of the agreement. But she added: "Once they saw what had been agreed overnight they realised that actually what we had all been telling them right the way through, which is that there was a goodwill on the part of the negotiators of the world to re-engage the United States constructively, they looked at the text, they saw that was true.

"They then suggested some other minor amendments that would make it more comfortable for them and that is why, in the end, we got agreement." The other key achievement at Montreal was that countries which have signed up to the Kyoto Protocol on greenhouse gas emissions agreed to set new targets when the treaty expires in 2012. Ms Beckett denied the overall outcome of the meeting had been "over-hyped" insisting it represented a "diplomatic triumph". She said it was a major achievement to bring 189 countries together in agreement. She was "extremely relieved, as well as delighted" the conference had achieved as much as it had.