The United States on Tuesday set the first nationwide carbon standards on power plants, seeking to curb emissions from the burning of coal and revive the flagging fight against climate change.

After more than a year of deliberations on the politically charged proposal, President Barack Obama's administration said it would only apply the rules to future sites and gave coal-fired plants decades to meet the new standards.

Lisa Jackson, head of the Environmental Protection Agency, said she was approving the regulations in a hope to "enhance the lives of our children and our children's children" and to spur US global leadership in clean energy.

"We know that the potential impact of climate change touches everything from tourism to agriculture and will have an extraordinary environmental and economic footprint if allowed to proceed unchecked," she told reporters on a conference call.

Jackson said that after a 12-month grace period for sites under construction, the agency would not allow power plants to emit more than 1,000 pounds (454 kilograms) of carbon pollution per megawatt hour.

Natural gas generates slightly less than that, but standard coal plants emit nearly 1,800 pounds an hour. Renewable energy such as solar and wind -- along with nuclear power -- produces far less.

Electricity generation in the world's largest economy accounts for 41 percent of the country's carbon emissions, which scientists blame for the planet's rising temperatures and increasingly severe weather.

The Obama administration has vowed to reduce US carbon emissions, but its efforts face strong opposition from industry and the rival Republican Party, many of whose members question the science behind climate change.

UN-led negotiations on a new climate treaty have also made little concrete progress, with China -- which has surpassed the United States as the top carbon emitter -- demanding greater US commitment.

Republican House Speaker John Boehner accused Obama of siding with a political base of environmentalists instead of Americans hit by high energy prices.

"This rule is a dramatic overreach and a heavy blow to one of America's richest natural resources -- coal -- that the president once heralded but now ignores," Boehner said in a statement.

Proposals by Obama's allies to set up a nationwide system to curb carbon emissions have died in Congress.

Democratic Representative Henry Waxman, an architect of the ill-fated climate legislation, called the power plant standards "a breakthrough" and praised Obama for "listening to scientists, not extremists who deny the existence of climate change."

Coal is among the most politically sensitive areas due to its impact on domestic employment. Coal accounts for about half of US power -- more than any other source -- but 81 percent of carbon emissions from the electricity sector, according to government data.

Jackson was quick to say that the Obama administration saw a future for coal, saying that it "will remain an important part of America's electricity generation mix."

She said that the agency will still allow new coal plants to maintain emissions above the limits if the operators agree that the level will average below the 1,000-pound threshold over a 30-year period.

The Obama administration has supported research into so-called carbon capture, which would hold back emissions from the burning of coal. Some environmentalists have criticized such efforts as costly and unproven.

Kassie Siegel of the environmental group the Center for Biological Diversity welcomed the new standards but criticized the administration for giving existing power plants "a free pass."

"If we're going to avert a climate catastrophe, the response must match the magnitude of the crisis we face," she said.