WASHINGTON (REUTERS) - The United States environmental regulators will likely delay finalising rules to limit carbon emissions from new power plants, a measure that has been one of President Barack Obama's top strategies to fight climate change, according to a report on Friday.

The rules had been proposed by the Environmental Protection Agency nearly a year ago. They are expected to be revised to set a separate standard for coal-fired plants, as opposed to natural gas-fired plants, according to the report from The Washington Post.

The administration had been expected to tackle emissions from existing power plants, which account for 40 percent of U.S. greenhouse gas emissions, after finalizing the rules on new plants, which had been expected in April.