The G8 agreed at a summit in this German seaside resort to pursue major cuts to dangerous greenhouse gas pollution and said they would "seriously consider" the goal of halving global emissions by 2050.

The deal brokered by German Chancellor Angela Merkel was a compromise which she admitted fell short of her target of a binding agreement to slash carbon pollution, in the face of US opposition to any mandatory targets.

Merkel said she was "very satisfied" and British Prime Minister Tony Blair called the deal "a major, major step forward."

But global warming campaigners said it came up far too short.

"These goals are a joke," said anti-globalisation group Attac, which organised days of noisy protests against the summit.

"The deal is clearly not enough to prevent dangerous climate change" said Daniel Mittler, climate policy advisor of Greenpeace International.

"The US isolation in refusing to accept binding emission cuts has become blindingly obvious at this meeting."

Greenpeace said G8 states need to slash emissions by at least 80 percent by 2050 to avoid catastrophic global warming.

"Chancellor Merkel and Prime Minister Blair are trying to portray this as a strong agreement. But President Bush didn't give them an inch," said Philip Clapp, president of the US National Environmental Trust.

"The best they could get from him was a statement that their 50 percent-by-2050 emissions reduction proposal would be 'seriously considered'. That's a pretty tiny landmark."

Yet many observers said the declaration signed by Britain, Canada, France, Germany, Italy, Japan, Russia as well as the United States opened a new chapter of international cooperation with Washington.

The UN's top official on climate change said the declaration was "everything I had hoped for" and suggested Washington had made significant concessions.

"Very recently, (the United States) indicated that it was too early, it was premature to begin negotiations on a post-2012 climate change regime, so that's a very clear shift," said Yvo de Boer, executive secretary of the United Nations' Framework Convention on Climate Change (UNFCCC).

Merkel said she thought US President George W. Bush's turnabout came "in light of massive scientific findings and many debates in Europe and the United States."

European media were overwhelmingly positive in their take on the pact.

"When the politicians pronounced a 'successful deal' on climate change at the G8 summit yesterday, they were naturally putting a positive gloss on an agreement which is still a long way from an iron-clad commitment to reduce greenhouse gases," The Times of London said.

"Yet to brand it rather scornfully as a 'compromise', as others have done, is to underplay the significant progress that has been made ... What matters is that America has clearly come in from the cold."

German newspapers credited Merkel's close ties with Bush as making the difference, in positive editorials across the political spectrum.

"Considering the point where they started, the compromise of the G8 summit is more than has been achieved in years of trying to achieve effective climate protection," Berlin's centre-left daily Tagesspiegel wrote.

"This success is thanks to Angela Merkel and her tenacity and the pressure of the American public."

The communique gave a spur to talks for a successor to the Kyoto Protocol -- the emissions-cutting pact which runs out in 2012 -- and spells out that any deal should be global and come under the auspices of the UN.

The Handelsblatt business daily said the pact marked the first time that the G8 had set a "magic number" for climate change but warned that the G8 states now needed to follow through.

"The goal 'minus 50 percent by 2050' is in the text even if there are several important restrictions," it said. "Remember -- the US government helped negotiate Kyoto. But the USA never ratified the pact."

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