A third U.S. rail union voted against a national contract made in September, and continues negotiating to reach a deal, according to Reuters. Labor unions are bargaining to improve sick leave and attendance policies. Two of the largest unions have yet to announce their votes.

Rail workers and railroads have until Dec. 9 to come to an agreement or the U.S. could again be faced with a potential strike. The International Brotherhood of Boilermakers rejected the deal on Monday. All twelve unions must approve the deal for it to be finalized.

If the unions can't approve the deal before Dec. 9, Congress might need to get involved by either pushing back the deadline or forcing a deal. "A rail shutdown could freeze almost 30% of U.S. cargo shipments by weight, stoke inflation, cost the American economy as much as $2 billion per day and unleash a cascade of transport woes affecting U.S. energy, agriculture, manufacturing, healthcare and retail sectors," reads the Reuters article.

The American Chemistry Council, representing companies such as 3M, Dow, Dupont, BP, Exxon Mobil and Eli Lilly, said the rail strike would impact a total of $2.8 billion in chemicals cargo a week, per CNBC. "A rail strike of one month could result in an economic impact of up to $160 billion, and within one week many chemical manufacturing plants could shut down, lowering GDP and leading to more inflation," reads an article from the news outlet.