The letter directs lawmakers in Washington to take up the Miners Protection Act before Congress closes out in 2016 session next month.
"This bill is simple- it is the continuation of a longstanding commitment by our government to lifetime health and retirement benefits to our miners," a portion of the letter said.
A downturn in the coal industry is jeopardizing the stability of the plan enacted in 1974.
A collection of coal miners from all parts of the country including Southwest Virginia rallied in Washington, D.C. in September as part of an event sponsored by the United Mine Workers of America to urge passage of the bill.
Later that month, the Senate Finance Committee voted 18 to 8 to recommend passage of the act.
More than 12,000 miners have already received notice that their health care insurance will be terminated at the end of the year because of the state of the fund