The U.S. is barreling toward a railroad strike this week that could cost the economy $2 billion a day and send food prices soaring even higher. Labor unions and freight railroads worked through the weekend trying to reach a contract but have yet to come to terms. Both sides have until Friday before workers are allowed to strike.

On Monday, railroads started delaying some hazardous and sensitive shipments to prepare for a possible stoppage “to ensure that no such cargo is left on an unattended or unsecured train,” the Association of American Railroads announced. That includes loads containing chemicals used in fertilizer.

Two of the largest labor unions involved blasted the move as an “unnecessary attack.” Presidents from the Brotherhood of Locomotive Engineers and Trainmen and the SMART Transportation Division said the railroads are “harming the supply chain in an effort to provoke congressional action.”

The two unions, which represent roughly half of railroad union workers, are holding out on a deal until policies on attendance, vacation and sick days are addressed. The unions claim members are getting fired for missing work due to illness and doctor visits.

A coalition of 31 agriculture groups have pressed Congress to intervene in the event of a work stoppage that they say would lead to “devastating consequences to our national and global food security” and “drastically make inflation worse.”

Congress can step in and extend the negotiating deadline or force a contract to prevent a stoppage. They last intervened in 1992, with former President George H.W. Bush signing the return to work bill two days into the strike.

Last month, President Joe Biden appointed a Presidential Emergency Board to help negotiate a compromise, but the closer both sides get to this Friday’s deadline, the more the president gets squeezed between a potential supply chain catastrophe and his promise to be the most pro-union president in American history.