By Valerie Volcovici

WASHINGTON (Reuters) - About 10,000 retired coal miners and their families descended on the U.S. Congress on Thursday to pressure lawmakers to pass stalled legislation that would prevent 22,000 of them from losing their pension and health benefits as soon as early 2017.

A bipartisan group of senators is trying to pass legislation to ensure the retirees' coverage with the United Mine Workers of America’s retirement and healthcare funds, which are dwindling as some coal companies drop benefits in their bankruptcy proceedings.

The future of the coal industry and its workers has been an issue in national politics. With just weeks to go before the presidential and congressional elections in November, time for passage of the bill is limited.

The union said the federal government was obligated to ensure coal workers continue to get the benefits. The UMWA pension currently supports about 120,000 former miners and their families.

“These miners put in decades of back-breaking work in America’s coal mines to energize our nation," UMWA International President Cecil Roberts said.

But some Republican senators, including Senate Majority Leader Mitch McConnell of Kentucky, have hesitated to support the legislation, either because they do not want to be seen bailing out unionized workers or because it does not address what they say is President Barack Obama's regulatory "war" on the coal industry.

Legislation backers say they are obligated to uphold a guarantee made in 1946 by President Harry Truman to protect the benefits to avert a strike.

Republican West Virginia Senator Shelley Moore Capito said on Wednesday that the payments were less than $600 a month.

"These aren't lavish pensions," she said. "This is food. This is the trip to see the doctor."

If Congress fails to pass the Miners' Protection Act, the $5 billion federal Pension Benefit Guaranty Corp, an agency that backstops failed private-sector pension programs and is already financially strained, would be responsible for the plans.

Story continues

Mervn Click, a retired coal miner from Hueytown, Alabama, who traveled more than 20 hours by bus for the rally, said his benefits could cease by year's end.

"I don't know what I will do if it runs out," he said as he stood under a tree facing the Capitol.

West Virginia Democratic Senator Joe Manchin said 46 Democratic senators and at least eight Republicans backed the bill. Three of the Republicans - Rob Portman of Ohio, Pat Toomey of Pennsylvania and Mark Kirk of Illinois - are up for reelection this November in tight races in coal-producing states.

Portman told the crowd he was confident the bill will pass in the Senate Finance Committee, where it will be discussed on Wednesday.

"We hope it's a strong vote because that will get it to the (Senate) floor like a torpedo," he said.

Senator Ron Wyden, an Oregon Democrat who is the ranking member of the Finance Committee, said he was "working both sides of the aisle" to make sure the bill gets passed.

"Today it's mine workers; tomorrow it can be woodworkers," he said, referring to his state's logging industry.

Democratic presidential nominee Hillary Clinton, who has criticized bankrupt coal companies for “shirking” their responsibility to pay healthcare benefits for retirees, voiced support for the bill.

“I firmly believe that if you spent your life keeping the lights on for our country, we can’t leave you in the dark," Clinton said in a statement.

She has also proposed a $30 billion package to help coal states adapt to a changing economy. That plan has been overshadowed by a comment she made earlier this year that she would put coal companies out of business.

Republican presidential nominee Donald Trump has repeatedly pledged to put coal miners back to work but has not offered any details. His campaign was unavailable for comment.

McConnell spokesman Robert Steurer told Reuters that the issue "deserves an open, transparent debate through regular order."

Vera Newton, a member of the United Auto Workers' Louisville, Kentucky, chapter joined her members at the rally in solidarity with the coal workers.

"If they lose this fight, we're next," she said. "It's like dominoes - if they lose their pension, other unions will follow."