In what Prime Minister Gordon Brown hailed as a major breakthrough ahead of the Copenhagen climate change conference in December, the European Union on Friday reached a “conditional” deal on funding efforts by developing countries to tackle global warming.

The EU agreed to a “fair” share of an estimated €100 billions a year needed by 2020 to fight climate change but, crucially, did not specify the amount.

The EU’s actual contribution would be “conditional” on how much other developed countries were willing to contribute and how the developing countries planned to spend the money.

Speaking after the deal was announced in Brussels, Mr. Brown said the EU was “leading the way with bold proposals”.

“We were aware that if the European Union did not come together to solve some of the impasses, the possibility of a deal at the Copenhagen summit would be a lot less likely,” he said.

European Commission President Jose Manuel Barroso said it would bring “new momentum” to the efforts to break the deadlock over a climate change agreement in Copenhagen.

“Next week, we’ll meet the U.S. President and will say ‘let’s make Copenhagen a success’,” he said.

But critics called it a “white-wash” and demanded that the EU specify its contribution.