The United States is getting most of the blame for stalling negotiations after insisting developing countries must also cut production of greenhouse gases.

This has irked countries like China which say they must have room for industrial growth to raise living standards.

BBC Environment Correspondent Robert Pigott: US wants poorer coutries to cut back too

However, Argentina's President Carlos Menem has broken ranks with other developing countries by agreeing to reduce emissions.

Delegates at the conference are trying to decide how to deliver on the 1997 Kyoto treaty, which calls for developed nations to cut greenhouse gas emissions to 5.2% below the 1990 level by 2012.

But the 180 participating countries remain deeply divided on solutions.

The three groups still in dispute represent competing trading blocs which are unwilling to take on expensive clean-up commitments that might leave them at a disadvantage with competitors.

BBC Environment Correspondent Richard Wilson says a fragile agreement is starting to emerge.

However, the final agreement must be approved by consensus and not by voting, making it impossible to deal with individual sticking points one at a time on a majority vote.

Our Correspondent says that at varying times during the night there have been as many as eight competing proposals in circulation.

The differences

• US and Europe disagree over emissions trading - countries selling excess allowances to those struggling to make cuts.
• European nations favour a tax making it harder for rich countries to buy permits abroad instead of making cuts at home.
• US says emissions trading should operate under free-market principles.

Differences have also been exposed between industrialised and developing nations over the best way forward.

More than 130 countries remain outside the scope of the Kyoto protocol.

• Large developed nations want voluntary commitments from developing nations to cut greenhouse gases.
• Poorer states say most damage is caused by the industrialised world. They say they should not have to pay, but should be allowed to increase their own emissions to improve living standards.

Warming warning

Most of the world's climate scientists agree on the urgent need to solve the problem.

Environmentalists satirise the US cash for emissions plan

They predict that the global temperature will rise by up to 3.5C over the next century - greater than any climate change in the last 10,000 years.

They say sea levels will rise by anything between 15cm and 95cm by 2100 - and will go on rising for another 400 years.

A number of governments, scientists and environmentalists at the meeting have also warned there could be more extreme weather.

US boost

Tim Hirsch in Buenos Aires: "America has stressed that the signing imposes no obligations"

The United States gave the meeting a boost on Thursday with its decision to sign the Kyoto agreement - it was the last major industrial nation to do so.

However, many environmentalists said it was an empty gesture.

The US Congress must approve the agreement but its Republican party majority opposes Kyoto's current form.

Kyoto agreed on three "mechanisms" to help to reduce the cost of making the reductions: