UN climate talks in Warsaw ran into overtime with countries arguing over the building blocks for a new global warming pact.

A draft text gave only vague direction on when countries should present their targets for restricting carbon emissions.

The draft said only that commitments should be presented "well in advance" of the Paris summit in 2015.

Disputes over when rich and poor nations will set greenhouse gas targets and over climate aid to the developing world have threatened to sink the talks and few concrete steps have emerged.

"The Warsaw talks, which should have been an important step forward ... are now on the verge of delivering virtually nothing," said China's lead climate negotiator Su Wei.

Around 800 representatives from 13 non-governmental organisations walked out on Thursday, exasperated at the lack of progress.

It was hoped the conference would at least produce a timetable to ensure that emissions cut targets and climate finance pledges were set in time for Paris.

But both the selection and wording of issues have been bitterly contested.

Rich countries want to set emission targets for all, while developing nations say industrialised nations must lead in setting targets and foot most of the bill because they have accounted for most emissions.

The talks have also been sharply divided over aid.

Developed nations agreed in 2009 to raise climate aid to $100 billion (£61.8bn) a year from 2020 from an annual $10bn (£6.18bn) for 2010-12.

But rich countries are now focused on their own embattled economies and are resisting calls to raise aid from 2013 to 2019.