Thousands of miners have rallied and marched in southwestern Pennsylvania to safeguard pensions and health benefits.
The United Mine Workers of America says it's concerned because environmental regulations on coal-burning plants have combined with abundant supplies of natural gas to drive down demand for coal at power plants.
Earlier this week, Virginia-based Alpha Natural Resources asked a bankruptcy judge to let it break a union contract so the company can reorganize its finances.
The union says Friday's rally and march from the Greene County Airport to the Greene County Fairgrounds was a "demonstration of solidarity" as the coal industry has dealt with down-sizing and bankruptcies.
The union says although judges can void contracts in bankruptcy court, the union must still agree to work under any amended contracts.