The US Environmental Protection Agency proposed to limit carbon dioxide emissions from new power plants in a bid to implement President Barack Obama's plan to fight climate change.
The move marks the "first milestone" of a major part of the Climate Action Plan announced in June by the US leader, the agency said in a statement.
"Climate change is one of the most significant public health challenges of our time," EPA Administrator Gina McCarthy said.
The plan foresees that new large natural gas-fired turbines meet a limit of 1000 pounds of carbon dioxide per megawatt hour, while new small natural gas-fired turbines would have to meet a limit of 1100 pounds of carbon dioxide during that same timeframe.
New coal-fired units, meanwhile, would not be allowed to exceed 1100 pounds of carbon dioxide per megawatt hour, with "the option to meet a somewhat tighter limit if they choose to average emissions over multiple years".
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Together, natural gas and coal-fired power plants account for roughly a third of all US greenhouse gas emissions.
The average advanced coal plant currently emits about 1800 pounds of carbon per hour, according to industry figures.
The proposed new standards, which will undergo a 60-day public comment period, also seek to ensure that new power plants are built with clean technology to keep emissions to a minimum, according to the EPA.
"These standards will also spark the innovation we need to build the next generation of power plants, helping grow a more sustainable clean energy economy," McCarthy said.
