World leaders pledged last week to step up efforts to reach a U.N. deal to fight climate change, but they will have to match rhetoric with rapid action to break a crippling deadlock before a December deadline.

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.

President Barack Obama, fresh from his first legislative victory on climate policy, expressed confidence on Monday that new greenhouse gas emission limits would become law with help from the U.S. Senate.

Obama also announced new measures on efficiency standards for lighting used in homes and businesses to take effect in 2012.

Climate change has already caused "visible impacts" in the United States and poses particular risks to the U.S. agriculture and energy industries, a new government report said on Tuesday.

The United States intends to work toward reducing emissions of potent greenhouse gases found in refrigerators and air conditioning systems but has not yet decided which international venue to use to advance the issue, US officials said on Monday.

The United States hopes to take the reins of international efforts to battle global warming next week with a meeting of major economies aimed at facilitating a UN pact to cut greenhouse gas emissions.

US President Barack Obama hopes to get a climate change bill on his desk this year and is open to discussing how stringent the rules of a carbon emissions trading system should be for industry, a top adviser said on Tuesday.

President Barack Obama will be flexible about climate change legislation moving through Congress, the White House said on Wednesday, indicating some wiggle room on his demand for full auctioning of carbon emissions permits to industry.

President Barack Obama said revamping U.S.

The United States is still working toward an agreement with G20 partners to phase out subsidies for fossil fuels, a top White House adviser said ahead of this week's G20 summit.

Michael Froman, deputy national security adviser and top G20 aide to President Barack Obama, said the United States was hoping to reach an agreement about the issue at the Pittsburgh summit on Thursday and Friday.