(The Hill) — Nearly 5,000 railway workers at the International Association of Machinists and Aerospace Workers (IAM) voted to reject a tentative contract agreement with railroads and authorize a strike, the union said Wednesday.

IAM members are the first to approve a strike and reject a contract based on recommendations released by a White House-appointed board last month. 

The vote reveals that rail workers are not satisfied with the agreement, which calls for 24 percent raises and back pay but doesn’t address workers’ demands for more predictable scheduling and the ability to take time off for doctors’ appointments without being penalized. 

IAM said that it would delay strike action until Sept. 29 at noon to allow union leaders to continue negotiations with railroads.

“We look forward to continuing that vital work with a fair contract that ensures our members and their families are treated with the respect they deserve for keeping America’s goods and resources moving through the pandemic,” IAM said in a statement.

More than 115,000 rail workers are legally allowed to strike as of Friday, a move that would shut down the transport of food, fuel and other goods, likely damaging the nation’s strained supply chains and driving up prices.

Lawmakers are preparing to use their authority to block a walkout. GOP senators are backing a bill that would enact a new contract based on the presidential board’s recommendations — the option railroads and other business interests are lobbying for — while Democratic leaders say they will intervene if necessary.

The White House, meanwhile, is discussing contingency plans to assure that key goods still make it to their destinations if railroads shut down. 

“We are working with other modes of transportation, including shippers and truckers, air freight, to see how they can step in and keep goods moving in case of this rail shutdown,” White House press secretary Karine Jean-Pierre told reporters Tuesday.