The UK government and environment groups have welcomed an international deal to tackle global warming, after climate change talks in Canada.
Delegates agreed to set new targets when the Kyoto treaty expires in 2012
Countries signed up to the Kyoto Protocol have now agreed to set new targets on greenhouse gas emissions when the treaty expires in 2012.
Prime Minister Tony Blair said the deal was a "vital next step in tackling climate change".
Friends of the Earth added the meeting had secured an "historic agreement".
Mr Blair said he welcomed the "progress" made in Montreal.
"This agreement is the result of years of hard work and is a vital next step in tackling climate change - the biggest long-term challenge facing the world.
"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.
Delegates at the United Nations conference on Climate Change in Montreal also agreed to adopt a rule book for Kyoto, formally making it fully operational after years of negotiation and ratification.
The United States, which had earlier walked out of the summit, has also agreed to take part in non-binding talks on long-term measures to combat global warming.
Environment secretary Margaret Beckett said while the UK and the EU would do their "utmost" to ensure the process would be a success, every country had to play its part.
"Of course this is only the beginning. But the fact that we have all been bold enough to express our commitment so clearly - that we are ready to take a fresh look at the problem, despite various fears and concerns, is a cause for great optimism," she said.
"We must also live up to the commitments we have made. We will do so.
"A subset of countries cannot do it all by themselves. In line with the principle of common but differentiated responsibilities and capabilities, we all have to play our part."
Environmental campaigners also welcomed the deal.
Friends of the Earth's (FOE) international vice chairman Tony Juniper said the meeting was a "historic agreement" that will "strengthen global resolve with legally-binding targets to take action to tackle climate change under the Kyoto Protocol".
"It has sent a clear signal that the future lies in cleaner and more sustainable technologies and is good news for people everywhere," he said.
Jonathan Porritt, who heads the Sustainable Development Commission, which advises the government on environmental issues, said the international community had come a long way on the issue of climate change.
"There's a different consensus emerging now. Not just amongst the existing signatories to Kyoto, but amongst the vast majority of countries, if not all countries that we have to push this further and faster," he told the BBC.
But the Tories said that Saturday's deal did not amount to much.
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."