US President Barack Obama is poised to unveil sweeping new limits on carbon emissions.

On Monday, the Environmental Protection Agency (EPA) is expected to unveil proposals for drastic cuts in carbon emissions from power plants, which account for 40 per cent of greenhouse gas emissions in the US.

“The shift to a cleaner energy economy won’t happen overnight, and it will require tough choices along the way,” Obama said on Saturday in his weekly radio and internet address.

“But a low-carbon, clean energy economy can be an engine of growth for decades to come.”

Even as natural gas gains in popularity, coal remains a key component in the American energy landscape. Wyoming leads the pack of 25 states that mine the fossil fuel, followed by West Virginia, Kentucky, Pennsylvania and Illinois.

Hundreds of coal-fired power plants dotted across the country provide about 37 per cent of the US electricity supply, ahead of natural gas (30 per cent) and nuclear reactors (19 per cent).

While the extent of the measures have yet to be disclosed, the main outlines are clear: the administration will set emissions reduction targets for each state and then give them leeway in meeting those caps.

On Sunday, The Wall Street Journal and The New York Times, citing sources briefed on the plan, said the EPA would seek a 30 per cent cut in carbon emissions by 2030, compared with 2005 levels.

States would be given several options for how to achieve the cuts, the reports said.

Climate change is a hot-button issue in American politics.

Republicans, who control the House of Representatives, are against any new law touching on it, with some even disputing the existence of global warming. Others cast doubt on whether humans are to blame for the phenomenon.

Stymied on the legislative front, the White House is now poised to act on a regulatory level via the EPA by evoking the Clean Air Act – an approach criticised by some industry advocates who warn such action could lead to major job losses.

This new initiative – which also aims to promote renewable energy sources such as solar and wind, as well as energy efficiency – is part of a larger climate action plan announced by Obama a year ago.

In his weekly address on Saturday, Obama defended his regulatory approach, stressing that climate change was “no longer a distant threat” but a reality.

“We limit the amount of toxic chemicals like mercury, sulfur, and arsenic that power plants put in our air and water. But they can dump unlimited amounts of carbon pollution into the air,” he said.

“It’s not smart, it’s not safe, and it doesn’t make sense.”