UK Environment Secretary Margaret Beckett has dismissed suggestions the UN climate control deal achieved in Montreal has been "over-hyped".
Margaret Beckett praised the "massive effort" involved
Mrs Beckett said she achieved all she set out to at the conference, which ended in agreement on two key issues.
Talks can now begin on new targets to reduce carbon emissions when the Kyoto treaty ends in 2012, and the US has agreed to non-binding talks on climate.
Forging agreement between 189 countries was "a diplomatic triumph", she said.
However, she revealed that just an hour before the deal was struck on Saturday, she feared talks would break down because the Americans were nervous about some of the details of the text.
She told the BBC's Sunday AM programme: "Once they saw what had been agreed overnight they realised 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."
She confirmed there had been "conversations to and fro between London and Washington" before the last-minute deal, but declined to say whether Prime Minister Tony Blair had spoken directly to US President George Bush.
'Vital next step'
The deal resulted in the US agreeing to take part in non-binding talks on long-term measures to combat global warming.
And countries signed up to the Kyoto Protocol have now agreed to set new targets on greenhouse gas emissions when the treaty expires in 2012.
Delegates agreed to set new targets when the Kyoto treaty expires in 2012
Prime Minister Tony Blair has said the deal was a "vital next step in tackling climate change".
"Of course it is only a beginning but it is important and demonstrates why it is always worth engaging with America and the rest of the world," he said.
Friends of the Earth said the meeting had secured an "historic agreement".
International vice chairman Tony Juniper said: "It has sent a clear signal that the future lies in cleaner and more sustainable technologies and is good news for people everywhere."
Delegates at the Montreal meeting also agreed to adopt a rule book for Kyoto, formally making it fully operational after years of negotiation and ratification.
Mrs Beckett added: "It has taken all year and a massive effort on the part of everybody involved from the prime minister on down, but we got there. We got everything we set out to get at the beginning. And that doesn't happen very often."
The Tories, however, have been sceptical of the deal.
Shadow environment secretary Peter Ainsworth said: "It's better than nothing, but it isn't much. We need a great deal more than talk if we are going to stop the descent towards rapid and irreversible climate change."
New Tory leader David Cameron has signalled a move to set up a policy group on the environment to pave the way for "tough decisions" on cutting greenhouse gas emissions.
Mrs Beckett said that if the Tories would not accept the government's proposals, they had to come up with something that would achieve similar objectives.