The Brotherhood of Railroad Signalmen (BRS), which represents over 6,000 rail workers, rejected a four-year labor deal Wednesday with 60.5% voting against a proposed agreement. The move raises concerns about a possible rail strike.

The National Carriers' Conference Committee, which represents freight railroads during labor deals, said it was "disappointed" by the vote.

The BRS vote is the second labor deal downvoted by a major railroad union, as The Brotherhood of Maintenance of Way Employees Division of the International Brotherhood of Teamsters (BMWED) union recently voted to reject a proposal by the freight railroad industry. BMWED represents about 23,000 track maintenance workers and is the third largest of the 12 freight rail unions.

The vote by BRS comes a little over a month since the Biden administration reached a tentative agreement with major U.S. railroads on Sept. 13.

President Joe Biden and Labor Secretary Marty Walsh had personally intervened and created a three-person Presidential Emergency Board (PEB) to assist in labor discussions.

Following the September agreement, Biden said, "You've reached an agreement that will keep our critical rail system working and avoid disruptions of our economy."

The agreement may be short-lived, however. Although only two unions have rejected the deal, any strike by a single union would be honored by the others, wreaking havoc on U.S. supply chains ahead of midterm elections and the holiday season. BMWED and BRS represent 25% of rail freight workers while the six unions which have ratified their deals represent about 20% of workers. Four unions have not yet voted on the deal.

The pending contract includes cash bonuses for union members of $1,000 a year and a 24% raise over a five-year period.

The most prominent disputes in the contract are over work conditions due to staffing shortages which require workers to be on call seven days a week. Union members are also stuck on the issue of sick leave which has not been included in the contract in favor of increased wages. BMWED attempted to propose sick leave after the union voted against the labor deal in September but the motion was rejected.

BRS President Michael Baldwin said the railroads and PEB "both failed to recognize the safety-sensitive and highly stressful job BRS members perform each day to keep the railroad running and supply chain flowing."

The rail unions have agreed to maintain the status quo until Dec. 9, allowing time for negotiations before the possibility of a strike which could have severe consequences for the economy.

Trains carry 40% of long-distance freight tonnage, leading some to pressure Democratic lawmakers to step in to force a compromise between the industry and unions.

Democratic leaders have so far declined to intervene.

If trains halt due to a strike it could lead to increased prices at a time when inflation is already rising and the economy is still attempting to recover from the pandemic.