The U.S. Chamber of Commerce on Monday called for "urgent action" in railroad labor negotiations to avoid a strike and a "national economic disaster."

The largest U.S. business association called on Congress to take immediate action if railroads and unions are unable to come to a voluntary agreement ahead of a possible work stoppage on Friday.

"A shutdown of the nation’s rail service would have enormous national consequences. It would lead to perishable foods such dairy, fruits, and vegetables spoiling at their points of origin, would halt Amtrak service ... disrupt materials and goods being delivered to factories and ports, and would inhibit the transport of heating fuel and other important fuels and chemicals," the Chamber said. "The costs of such a shutdown to the U.S. economy could come out to $2 billion per day."

The White House did not immediately comment.

On Sunday, two unions negotiating contracts for almost 60,000 workers at major U.S. freight railways said those employers are halting shipments of some cargo to gain leverage ahead of this week's deadline to secure labor agreements.

As of Sunday, eight of 12 unions had reached tentative deals, the National Railway Labor Conference (NRLC) said. Those groups do not include SMART-TD and BLET, which represent about half of the 115,000 workers affected by the talks. Three unions reached agreements on Sunday.

Unions and railroads, including Union Pacific, Berkshire Hathaway's BNSF, CSX, and Norfolk Southern, have until a minute after midnight on Friday to reach tentative deals. Failing to do so opens the door to union strikes, employer lockouts, and congressional intervention.

Railroads late last week said they would begin halting shipments of hazardous and toxic materials starting on Monday to ensure safety in the event of a strike.

The brinkmanship comes at a sensitive time for unions, railroads, shippers, consumers, and President Joe Biden - who appointed an emergency board to help break the impasse.

Widespread railroad disruptions could choke supplies of food and fuel, spawn transportation chaos, stoke inflation, and cause $2 billion per day in lost economic output.