WRAPUP 1-G8 set for showdown with poorer states over climate

(For more G8 summit stories, click on [G7/G8])

* G8 set for climate change showdown

* Poor states unimpressed by G8 plan to curb greenhouse gases

* Two sides may clash over global trade as key talks loom

By Yoko Kubota and Oleg Shchedrov

TOYAKO, Japan, July 9 (Reuters) - Big emerging economies will come under pressure on Wednesday to respond in kind to an initiative by rich countries to work towards a target of at least halving their global greenhouse gas emissions by 2050.

The Group of Eight (G8) industrial nations want the leaders of eight fast-growing countries to adopt a "shared vision" of tackling global warming in U.N. negotiations due to conclude in Copenhagen in December 2009.

"There has been major progress on the climate change agenda beyond what people thought possible a few months ago," British Prime Minister Gordon Brown said of Tuesday's agreement.

"For the first time the G8 has said we will adopt at least a 50 percent reduction in carbon emissions by 2050 as part of a worldwide agreement that we hope to get in Copenhagen," he said.