President Joe Biden on Monday called on Congress to vote on legislation that would prevent a rail strike.

“I am calling on Congress to pass legislation immediately to adopt the tentative agreement between railroad workers and operators—without any modifications or delay—to avert a potentially crippling national rail shutdown,” Biden said in a statement released by the White House.

The tentative agreement, which House Speaker Nancy Pelosi said the U.S. House would vote on this week, was reached by rail and union negotiators in September.

But since that deal was reached, four unions have rejected its terms, according to the American Association of Railroads. Eight of the 12 railroad labor unions have voted to ratify the deal.

“On the day that it was announced, labor leaders, business leaders and elected officials all hailed it as a fair resolution of the dispute between the hard-working men and women of the rail freight unions and the companies in that industry,” Biden said.

The U.S. economy relies on freight railroads to carry about 30% of the nation’s cargo, including large quantities of food, fuel and chemicals that cannot be transported in other ways.

The impact of a strike on the country’s economy would be staggering—$2 billion a day, devastating the economy, the Association of American Railroads noted.

“Without freight rail, many U.S. industries would shut down. My economic advisors report that as many as 765,000 Americans—many union workers themselves—could be put out of work in the first two weeks alone,” Biden said in the statement. “Communities could lose access to chemicals necessary to ensure clean drinking water. Farms and ranches across the country could be unable to feed their livestock.”

The strike threat comes amidst already poor—though improving slightly—rail service conditions, a long-term truck driver shortage and dangerously low water levels on the Mississippi River.

More than 300 agriculture-related organizations, including the American Farm Bureau Federation (AFBF), urged Biden to continue to work with the railroad unions and railroads to ensure that the tentative agreement he helped broker this summer is ratified by the parties.

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