Negotiators from Europe, tiny islands threatened by rising oceans and the world's poorest countries sought to keep alive the only treaty governing global warming and move to the next stage, struggling against an unlikely alliance of the United States, China and India.

Bleary-eyed delegates worked through the night and all day on Friday, and the two-week U.N. conference stretched past the hour it was supposed to end, with the negotiators looking ahead to a second and final night of meetings expected to last until dawn Saturday.

Delegates from the 194-party conference are trying to map out the pathway toward limiting global emissions of greenhouse gases for the rest of this decade, and then how to continue beyond 2020.

Scientists say that unless those emissions — chiefly carbon dioxide from power generation and industry — level out and reverse within a few years, the Earth will be set on a possibly irreversible path of rising temperatures that lead to ever greater climate catastrophes.

The European Union said after a negotiating session of 26 key ministers that lasted beyond 4 a.m. Friday that support was growing for its plan to negotiate a new accord for a post-2020 world.

But the optimism faded as the day wore on and the three holdouts held firm. More than 120 climate-vulnerable countries signed on to the EU vision calling for all countries to be held accountable for their carbon emissions in the future, not just the industrial countries.

The U.S., China and India, all for slightly different reasons, refused. European climate commissioner Connie Hedegaard said she was encouraged by progress overnight, but warned that if the three largest polluters stand fast, 'I don't think that there will be a deal in Durban.'

"It's a strange world when the U.S. is aligning with China and India to block action on global warming," said Jake Schmidt of the New York-based Natural Resources Defense Council.

A noisy demonstration of dozens of chanting, singing and horn-blowing protesters — all activists accredited to attend the conference — tried to disrupt a plenary meeting but were blocked by a phalanx of blue-shirted U.N. guards.

Ten protesters, including Greenpeace director Kumi Naidoo, were barred from entering the building for the rest of the conference.

"Leaders have been sleepwalking us into a crisis of epic proportions," Naidoo told The Associated Press. The protest was meant to "inject some urgency into the process."

It was the latest and largest protest at the conference this week. An American college student and six Canadians had their credentials withdrawn after heckling speakers from their countries in the plenary hall.

Under discussion in the back rooms was an extension of binding pledges by the European Union and a few other industrial countries to cut carbon emissions under the Kyoto Protocol. Those commitments expire next year.

The EU, the primary bloc bound by commitments under the 1997 protocol, conditioned an extension on starting new talks on an accord to replace Kyoto, at the latest by 2020. It insists the new agreement equally oblige all countries to abide by their emission targets.

Developing countries were adamant that the Kyoto commitments continue since it is the only agreement that compels any nation to reduce emissions.

Industrial countries say the document is deeply flawed because it makes no demands on heavily polluting developing countries. It was for that reason the United States never ratified it.

After adjourning after 4 a.m. Friday, conference president Maite Nkoana-Mashabane, who is South Africa's foreign minister, drafted a one-page compromise on the key question of the legal form of a post-2020 regime. The wording would imply how tightly countries would be held accountable for their emissions.

The draft called for launching a negotiating process "to develop a legal framework applicable to all" after 2020.

But the language proved too soft for the Europeans, and Nkoana-Mashabane was drafting a new formula.

Both China and the U.S. have said publicly they would be amenable to the EU proposal to negotiate a post-2020 agreement, but each attached tough conditions.

The United States is concerned about conceding any competitive business advantage to China. Beijing is resisting any suggestion to change its status as a developing country, saying it still has hundreds of millions of impoverished people.

India, which lags behind China in development even though its economy also is expanding rapidly, was taking 'a relatively tough stand here,' Hedegaard said.

Negotiators said India and the U.S. softened their positions during the day, but that China has refused to affirm its future commitments will be regulated under the foreseen international regime.

The U.S., where climate change is a delicate issue for the administration of President Barack Obama, says it does not want to agree that it will accept binding commitments as part of a deal that has not yet been negotiated.

The content of the deal is more important than its legal standing, U.S. envoy Todd Stern has told reporters. Under Kyoto, rich countries are legally bound to reduce carbon emissions while developing countries take voluntary actions.

Hedegaard said the EU's proposal was intended to dismantle the 20th century division of the world into camps of rich and poor, and to make adjustments that reflect the realities of the 21st century balance of economic power — and emissions.

Three Kyoto countries — Japan, Canada and Russia — already have announced that they will not extend their reduction commitments for another period because of Kyoto's imbalances.

If the EU fulfills its threat against renewing its pledges, that would not mean it would halt actions to reduce emissions.

The 27-nation union already has legislated a requirement to lower emissions to 20 percent below their 1990 levels by 2020, and has adopted energy efficiency targets and a plan for renewable energy that will proceed regardless of its international obligations.