BRUSSELS, Belgium – European Union leaders struggled Thursday to salvage ambitious plans to cut greenhouse gas emissions and switch to renewable energy, despite a widening economic slump that has cast doubt on the continent's groundbreaking commitment to go green.

German Chancellor Angela Merkel said the EU's biggest economic power wanted an unequivocal commitment to the plan despite the economic downturn. But Italy's premier threatened to veto the deal, and the 27 EU leaders will have a tough time finding a compromise that satisfies the often-conflicting demands from national industries.

The leaders were expected to approve an economic stimulus plan designed to inject euro200 billion ($258 billion) into the region's limping economy.

Shortly before the leaders arrived, Belgian police arrested 14 suspected al-Qaida-linked extremists they said might have been planning attacks. They did not say if the summit was a target.

EU governments have agreed to so-called 20-20-20 targets: reducing greenhouse emissions by 20 percent and ensuring that 20 percent of energy comes from wind, sun and other renewable sources by 2020.

But filling in the details and assigning national targets is problematic. As is rallying others — notably the United States, China, India, Russia and Brazil — into a global agreement under debate at a U.N. conference in Poznan, Poland.

Officials at the 12-day U.N. conference reported no real new commitment this week to cutting carbon emissions. An EU agreement could galvanize the global climate talks — but if the European leaders fail to agree, that could seriously slow U.N. efforts to forge a successor to the Kyoto Protocol on curbing global warming.

French President Nicolas Sarkozy, the host of the two-day EU summit, pledged to make "all efforts" for an EU climate deal.

Poland's minister for European affairs, Mikolaj Dowgielewicz, said a French draft plan circulating Thursday showed "progress, but it's not sufficient progress to arrive at a compromise today."

Poland is leading coal-dependent eastern European members in lobbying to scale back the EU's climate-change commitments, while Italy feels that expensive climate-change goals should be relaxed in favor of immediate economic needs.

France is suggesting several opt-outs to the strict reductions it wants industries to make, giving more free-trading permits to steel makers or cement producers that risk fleeing abroad to regions with looser environmental rules.

It also proposes leeway for countries very dependent on coal and oil for power generation — but insists that this must be temporary.

At the Poznan conference, U.N. Secretary General Ban Ki-moon appealed for the EU to stick to its ambitious goals.

"We look for leadership from the European Union," said Ban. "The decisions currently being made by European leaders in Brussels are (of) great consequence for the whole world."

Separately, the EU leaders pushed Ireland into holding a second referendum on the Lisbon Treaty — a blueprint for reforming the EU that supporters say is essential for the bloc to work effectively. The project has been on hold since Irish voters rejected it in June.