EU delegates have been working through the night to try to hammer out how much aid the bloc will give to developing nations to tackle global warming.

On the first day of a two-day summit in Brussels EU leaders had wanted to agree a joint offer of about 6bn euros ($9bn; £5.5bn) over three years.

But analysts say wealthier states are struggling to convince poorer Eastern European countries to contribute.

An EU pledge could boost chances of a deal at UN climate talks in Copenhagen.

The BBC’s Jonny Dymond in Brussels says that when the prime ministers and presidents restart their summit in Brussels later on Friday, they will find out whether a long night of arm-twisting has borne fruit.

“We will have a better figure tomorrow than we had tonight,” Swedish Prime Minister Fredrik Reinfeldt told a news conference late on Thursday.

“Over half the member states have made pledges and we will work through the night to see how far much further we can get and what countries can do in the form of voluntary contributions.”

‘Swift decisions’

The money being sought at the Brussels summit is for a “fast start” contribution to help the world’s poorest nations tackle rising sea levels, deforestation, water shortages and other consequences of climate change between 2010 and 2012.

I call upon you – put a figure on the table. We demanded this in the European Parliament resolution in November Jerzy Buzek, President of the European Parliament Climate pressures cloud EU summit EU climate package explained France gets key Commission job

Several wealthy EU states have announced significant contributions, but it is not yet clear what Germany, France and Eastern European nations are ready to contribute.

As the summit got under way, pledges had been made for around 2bn euros.

The largest contributions came from Britain at 883m euros and Sweden – which currently holds the rotating EU presidency – at 765m euros. The Netherlands has pledged 300m euros and Denmark 160m.

The figures are totals spread over three years – 2010-2012.

President of the European Parliament Jerzy Buzek told EU leaders that “swift, binding, global decisions” were also needed on climate targets.

“I call upon you – put a figure on the table. We demanded this in the European Parliament resolution in November,” he said.

Meanwhile in the US, a bipartisan Senate group has proposed the framework for a new climate bill.

The senators hope the framework will form a compromise and be in line with a bill that narrowly passed the House of Representatives in June.

The proposal suggests cutting carbon emissions by 17% by 2020 from 2005 levels.

Bankers’ bonuses

As EU leaders arrived for the Brussels summit there was a moment of drama when Greenpeace activists breached the security cordon disguised as an official delegation.

Greenpeace activists breached security at the summit by dressing as delegates

They held up banners reading “EU: Save Copenhagen” before they were moved aside by security guards.

Financial matters will also be discussed at the twice-yearly summit.

Earlier on Thursday, momentum was building for a tax on bankers’ bonuses. The leaders of France and Germany swung behind the idea after the UK announced a one-off supertax on bonuses in a pre-Budget report.

The enormous level of Greece’s debt will also be a concern.

Greek Deputy Finance Minister Philippos Sachinidis said it stood at 300bn euros – its highest level in modern history.

EU Commission president Jose Manuel Barroso said on Thursday he was confident Greece would overcome its problems.

The European Council meeting is the first since the Lisbon Treaty came into effect and Belgium’s Herman van Rompuy was elected as its first president.