Merkel said she had doubts that the Group of Eight most industrialised countries would reach an understanding on combating global warming at the June 6-8 summit because not all members of the club attached equal importance to the matter.

"At European level we have managed to send a very clear signal, but at an international level the interest in the issue is very different. This was clear at the EU-US summit in April," she said in a speech to the lower house of parliament.

Merkel said she was pessimistic that the summit in the Baltic Sea resort of Heiligendamm would result in a commitment to cut greenhouse gas emissions.

"As the G8 we must come to a common understanding on how we can fight climate change. But as I stand here today, I am not sure that we will manage this in Heiligendamm.

"We have to agree on how we will proceed to achieve this after the Kyoto Protocol runs out in 2012," she said.

The United States, the world's biggest producer of greenhouse gases, refused to ratify Kyoto, which was the first accord mandating cuts in the harmful gases.

Washington is now reportedly planning to stonewall German efforts to secure a pledge at the G8 summit to cut emissions by half by 2050.

With China set to overtake the United States as the number one emitter of greenhouse gases, Merkel said the G8 will also seek to get major developing nations to join the fight against climate change.

"The G8 wants to expand cooperation with emerging nations on the environment... If not, there will be no climate protection."

The chancellor said helping Africa overcome poverty was the other main challenge for the summit, and vowed that the G8 would honour pledges to increase aid to the world's poorest continent made at its 2005 summit in Gleneagles, Scotland.

"We will keep to these promises. The time has come to implement and our credibility is at stake," she said.

In the run-up to the June summit, anti-poverty campaigners have accused the G8 nations of falling behind on their promise to double aid to Africa by 2010 and petitioned Merkel to turn the situation around.

But the German chancellor warned African leaders that the time had come for them to drive through reforms. "If not, the help will not reach the people and this will be fatal," she said.

Merkel for the second time this week strongly criticised President Robert Mugabe's regime in Zimbabwe and the recent election chaos in Nigeria.

She said the G8 planned to press for the deployment "at last" of a joint United Nations-African Union force in Darfur to end the suffering of people caught in civil war since 2003.

The Sudanese government has repeatedly rejected international calls to allow UN peacekeepers into the region.

Turning to the global economy, Merkel again called for greater transparency on hedge funds and progress in the stalled Doha round of world trade talks, where she said "a breakthrough is still possible".

Germany is leading a campaign to rein in the trillion-dollar hedge fund industry, saying that tighter regulation is needed because a collapse of one or two of these funds could trigger an economic meltdown.

"Debate about transparency for hedge funds is indispensable," Merkel said.

However, some of Germany's G8 partners, most notably the United States and Britain, where most of the hedge funds are operated, reject the idea of regulation in the sector.

The G8 summit will be attended by the leaders of Britain, Canada, France, Germany, Italy, Japan, Russia and the United States.

African leaders who have been invited to participate include the presidents of Algeria, Egypt, Ghana, Nigeria, Senegal and South Africa.

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