California Governor Arnold Schwarzenegger is ready to put his star power to work for President Barack Obama on the environment when his own term ends next year, the former movie actor said on Thursday.

Mayor Antonio Villaraigosa wants to make Los Angeles the "cleanest, greenest big city" in the United States, but a key project to bring renewable energy across the desert to the city could change under pressure from environmental groups.

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.

The U.S. government on Tuesday awarded $550 million in grants to develop renewable energy projects to help double U.S. renewable energy production over the next few years, an Obama administration goal.

The grants will pay cash to companies in lieu of tax credits to support solar, wind, biomass and other renewable energy production facilities.

As the United States' power grid becomes more sophisticated, electricity rates will need to rise to reflect periods of intense energy use and to encourage consumers to change their electricity habits, U.S. Energy Secretary Steven Chu said on Monday.

Some 100 heads of state gathered at the United Nations on Tuesday for an unprecedented daylong conference on combating climate change, with key leaders like presidents Hu Jintao of China and Barack Obama acknowledging that agreement is an important goal, but also stressing their own needs.

Canada's wind power companies are getting a lift from rising oil prices, a healthier economy and energy-friendly government policies, even as tight capital markets continue to curb the recovery of the fledgling sector.

Solar power makers will get a boost in California, already their largest U.S. market, as it sharpens its focus on small-scale projects as part of efforts to get a third of its power from renewable energy.

Rules to add costs to fuels that emit the highest levels of carbon dioxide would deny millions of Americans access to stable Canadian energy and add to the nation's security risks, an interest group backed by oil companies said Thursday.