Developing countries today agreed to resume climate change negotiations in Copenhagen after a half-day suspension.
The G77 group, led by African countries, staged a walkout over accusations that richer countries were seeking to use the UN-sponsored conference to dodge their obligations to cut carbon emissions.
Poorer countries fear that the Copenhagen talks will kill off the 1997 Kyoto Protocol, which committed industrialised states to reduce greenhouse gases, with financial penalties for failure.
Their call for an extension of Kyoto is opposed by some industrialised states because the US - the second-largest emitter after China - remains outside the process, having refused to ratify the protocol.
Today's suspension of work came as Climate Change Secretary Ed Miliband acknowledged that the 192-nation conference was "not yet on track for the kind of deal we need" and said "more urgency" was needed to solve problems.
Speaking in Copenhagen, Mr Miliband urged delegates to make progress before national leaders arrived later this week.
"I think that the very clear message for negotiators and ministers is we need to get our act together and take action to resolve some of the outstanding issues that we face," he said.
Downing Street announced today that Prime Minister Gordon Brown would fly to the Copenhagen conference tomorrow - two days earlier than planned - to throw his weight behind efforts to reach a deal.
Mr Brown has already identified the need to help developing countries mitigate carbon emissions and adapt to the impact of global warming as one of the key elements to any agreement.
The PM's spokesman today said Mr Brown remained "optimistic" that a political deal could be reached by Friday.
The G77's chief negotiator Lumumba Stanislaus Di-Aping, from Sudan, said that today's walkout was prompted by the failure of the Danish presidency to put industrial nations' emissions targets at the top of the agenda.
Mr Di-Aping told BBC Radio 4's World at One: "We decided to stop and reflect on what is happening, because it had become clear that the Danish presidency - in the most undemocratic fashion - is advancing the interests of developed countries at the expense of the balance of obligations between developing and developed countries.
"What we want is a process that is democratic, that allows us full participation, that ensures the safety and lives of the developing countries in Africa and small island states.
"We want a deal that will save the Kyoto Protocol and we want finance and mitigation targets and commitment periods signed at this conference. If that doesn't happen, I am afraid we can't accept the idea that we are going to create a new legal instrument."
He added: "The EU in particular is pursuing a strategy of killing the Kyoto Protocol, hiding behind the US. Their issue is that they don't want to commit to ambitious targets commensurate to the risk."
Campaigners said that the developing countries were right to focus attention on the issue of carbon cuts in rich-world industrialised states.
Jeremy Hobbs, executive director of Oxfam International, said: "Africa has pulled the emergency cord to avoid a train crash at the end of the week. Poor countries want to see an outcome which guarantees sharp emissions reductions, yet rich countries are trying to delay discussions on the only mechanism we have to deliver this - the Kyoto Protocol.
"This not about blocking the talks - it is about whether rich countries are ready to guarantee action on climate change and the survival of people in Africa and across the world."
Nelson Muffuh, Christian Aid's senior climate change advocacy co-ordinator, said: "Africa has been driven to this by the lack of progress on key substantive issues such as strong mitigation targets, and the lack of offers of financial support from rich countries to poor to help them deal with climate change.
"We need far more robust emission targets from wealthy countries and much more finance."
Following the resumption of talks, International Development Secretary Douglas Alexander said: "Time is now against us in Copenhagen and we need leadership, not brinkmanship, to secure a deal to save the planet.
"Today's temporary suspension reminds us all of the real risk of failure. We need all countries around the negotiating table at all times to make progress."
Speaking in Copenhagen, Mr Alexander said Britain was "working hard to ensure that a firm and fair deal is on the table when world leaders arrive later this week".
And he added: "We recognise that emerging countries have the right to build up their industries and that the developed world has been the biggest contributor to the emissions which cause global warming. But we will not get an agreement unless everyone - developed and developing - plays their part.
"It is the moral responsibility of everyone round the negotiating table to work relentlessly for a fair, ambitious and effective deal in the hours and days ahead."