WASHINGTON (Reuters) - President Barack Obama, buoyed by a domestic victory on climate policy, faces his first foreign test on the issue next week at a forum that could boost the chances of reaching a U.N. global warming pact this year.

Obama, who has pledged U.S. leadership in the fight against climate change, chairs a meeting of the world's top greenhouse gas emitters at the G8 summit in Italy on July 9.

Known as the Major Economies Forum, the grouping includes 17 nations that account for roughly 75 percent of the world's emissions, making any agreement from its leaders a potential blueprint for U.N. talks in Copenhagen in December.

Meetings of the forum, which Obama relaunched earlier this year, have so far failed to achieve major breakthroughs.

Developing countries want their industrial counterparts to reduce emissions by 25 to 40 percent below 1990 levels by 2020, while rich nations want developing states to commit to boosting their economies in an environmentally friendly way.

Those debates and others will be featured at the Italy meeting, the first at a heads of state and government level, and all eyes will be on Obama, whose climate initiatives European leaders have lauded while privately pressing him for more.

Europeans "want to seize this moment to push as hard as they can on the Americans to get significant ... targeted commitments on carbon emissions reductions," said Heather Conley, a senior fellow at the Washington-based Center for Strategic & International Studies.