U.S. President George W. Bush (right) looks past German Chancellor Angela Merkel in the direction of Russian president Vladimir Putin during their official G8 summit photograph taken in Heiligendamm, yesterday. Bush sought to calm tensions with Moscow yesterday ahead of a meeting with Putin. - Reuters

World leaders meeting in Germany have agreed to pursue 'substantial' cuts in greenhouse gases, Chancellor Angela Merkel said yesterday.

Group of Eight (G8) powers failed to overcome United States resistance to committing to specific numerical targets to curb global warming, but did refer to the goal of some countries of cutting emissions by 50 per cent by 2050.

"In terms of targets, we agreed on clear language ... that recognises that (rises in) CO2 emissions must first be stopped and then followed by substantial reductions," Merkel told reporters at the G8 summit in the Baltic coast resortof Heiligendamm.

The summit text confirmed that the world's leading industrialised nations would act to stem the rise in global warming gases, followed by 'substantial' reductions, the most serious commitment to action on the issue by the United States, the world's largest global warmer.

Washington had resisted attempts by Merkel to set a firm goal for cuts needed to combat a warming of the earth's surface that scientists say risks swelling sea levels and causing more droughts and floods.

But she secured a partial victory by securing an inclusion of the target in the text.

The European Union believes 50 per cent cuts are needed to ensure that global temperatures do not rise more than 2 Celsius (3.6 Fahrenheit) above pre-industrial levels, a threshold it says will trigger "dangerous" changes in the climate system.

Merkel is hosting three days of talks at a Baltic coast resort with counterparts from Britain, Canada, France, Italy, Japan, Russia and the United States.

Environmentalists condemned the G8's failure to agree on specific, binding goals.

"Agreeing on a numerical target is a significant first step, and not taking that first step is going to condemn us to a lot of pain and suffering in terms of the impacts of climate change," said Neil Adger of Britain's Tyndall Centre for Climate Change Research.

G8 leaders are tackling other threats to global stability, including increased tension between the United States and Russia which some have said heralded the start of a new Cold War.

Security remains tight around the summit venue, a luxury hotel in the small seaside town of Heiligendamm.

Yesterday morning police power boats chased down several smaller Greenpeace craft trying to break through the security cordon, ramming one and dumping its occupants into the Baltic.

- Reuters