The Senate Finance Committee approved the measure Wednesday, 18-8.
Six Republicans, including Finance Chairman Orrin Hatch of Utah, joined all 12 Democrats in endorsing the bill. Supporters say it would save lives and honor a 70-year-old promise made by the federal government.
The measure has divided coal-state Republicans. Several endangered Republican incumbents support the bill, but GOP leaders — including Senate Majority Leader Mitch McConnell of Kentucky — are wary of bailing out unionized workers.
The bill would ensure retired miners receive more than $250 million a year in benefits now at risk amid the coal industry's steep decline and bankruptcies of several large companies.