Patriot Coal has notified employees of job cuts at two mining operations at the Corridor G complex near Danville, West Virginia.
The two mines are Hobet 21 mine and Beth Station preparation plant, where the company employs 360 people.
Under the WARN Act, the company was required to give a 60-day notice period to all employees who may be affected.
Patriot Coal president and CEO Bennett K. Hatfield said: "The combination of increasing EPA regulations, mild summer weather and low natural gas prices has resulted in thermal coal pricing at levels below operating costs at many Appalachian mines.
"Over the next two months, Corridor G management will further evaluate operations and staffing to assess their ability to produce coal at lower costs and determine the extent of actions to be taken. We deeply regret the impact these actions will have on our hard-working employees and neighbouring communities."
In 2013, the Corridor G mining complex produced 2.3 million tonnes of thermal coal.
Reacting to Patriot's WARN Act notice, West Virginia Governor Earl Ray Tomblin said: "The announcement of potential lay-offs at the Hobet 21 mine and Beth Station preparation plant is more tragic news for our miners and their families.
"We continue to hold out hope that the end result is not as severe as today's announcement, however we are committed to providing workforce training, continuing education opportunities and other assistance our miners and their families many need during this unfortunate time."
The company also issued similar notices to approximately 100 workers in April this year.
"We recognise market trends can play a part in these potential closures; however these trends also reflect the regulatory environment in which industry must operate," Tomblin added.
"We continue our fight for West Virginia's mining jobs and urge the EPA to reconsider its proposed plan and realise the real impact their proposed CO2 rules would have on West Virginia miners, their families and our communities."