This year will be the first time in history natural gas overtakes coal as the main source of electricity, the U.S. Energy Information Administration reports.

"In EIA's forecast, natural gas provides 33 percent of generation in 2016 while coal's share falls to 32 percent," the administration said in a short-term market forecast.

The U.S. Interior Department in January announced the start of a review of the federal coal program to identify potential reforms. While the review is ongoing, the Interior Department is pausing new coal leasing on public lands, with continued mining under existing leases. The review process is expected to take three years.

Natural gas is becoming the primary source of electricity in the nation. Prior to April 2015, the total monthly share of electricity generated by coal had always been greater than gas.

Apart from federal considerations on cleaner power sources, the EIA's report said coal has started to drop off in favor of natural gas because of lower costs. During an eight-year period ending in 2008, coal was less expensive than natural gas and helped coal dominate the energy landscape. Since the onset of the shale era in 2009, the price gap narrowed.

The Supreme Court stayed implementation of the federal Clean Power Plan pending ongoing litigation. Nevertheless, EIA said some coal-plant operators will be faced with moving away from coal use or retiring plants altogether.

EIA estimates total U.S. coal production will decline 3 percent this year as the country pushes a low-carbon agenda.