BRUSSELS (AFP) - The United States must do more to tackle climate change, Swedish Prime Minister Fredrik Reinfeldt said, in a challenge to President Barack Obama ahead of a key international summit in Pittsburgh.

"I hope to speed up the talks all over the climate issue," Swedish Prime Minister Fredrik Reinfeldt said in online comments, the day before a EU summit Brussels.

While acknowledging a promise by Japan's incoming prime minister, Yukio Hatoyama, to target 25 percent cuts in greenhouse gas emissions, Reinfeldt has been less impressed by Washington's efforts so far.

"We need also clearer signals from the United States on mitigation efforts," as well as other parts of the developed world, Reinfeldt said.

The European Union prides itself on taking the lead in the battle against climate change, with member states agreeing to make 20 percent cuts in CO2 emissions by 2020 from 1990 levels.

EU leaders are seeking a more ambitious global goal at international climate change talks in Copenhagen in December, and are ready to commit to 30 percent cuts if the rest of the world does likewise to attain the overall goal of restricting global warming to two degrees Celsius.

UN negotiations are tasked with delivering a treaty in Copenhagen to curb the emissions that feed global warming and help developing nations cope with drought, flood and rising sea levels.

"We are worried because the sum up of the initiatives taken so far is not enough to meet the two degree target," said Reinfeldt.

On top of that he stressed the need for the financial commitments to support those efforts and adapt to the climate change which is already inevitable.

In a draft communique drawn up for the EU summit on Thursday, European leaders underline that "each country that has not yet done so should make urgently ambitious commitments to mid-term reductions and quantifiable actions" on greenhouse gases.

Money set aside for the climate fight "will need to be scaled up urgently and substantially" adds the statement, seen by AFP.

Richer nations should also "contribute to financing the fight against climate change in developing nations," it continues.

State funding should be made according to "ability to pay and responsibility for emissions," the draft says.

The European Commission estimates that the cost of fighting global warming for developing countries will reach 100 billion euros (147 billion dollars) annually by 2020.

However, European diplomatic sources said some EU nations, including the Czech Republic, Hungary and Italy were unhappy at fixing figures for such aid before the bloc had even decided how to distribute climate funding among themselves.

Pressure is mounting for a breakthrough in what has been dubbed "Climate Week," which also kicks off in Washington on Thursday and Friday with a ministerial-level gathering of the world's 17 largest carbon polluters.

On Tuesday, UN chief Ban Ki-moon will host a climate summit in New York, to be followed by a two-day Group of 20 summit in Pittsburgh, Pennsylvania on September 24-25.