Train and engine service members of the transportation division of the International Association of Sheet Metal, Air, Rail, and Transportation Workers (SMART-TD) voted to reject a recent deal brokered by government representatives, Reuters reports. 

Unions expressed discontent with paid sick leave conditions, according to the outlet.

SMART-TD, which includes conductors, brakemen and other workers, joins three other unions in declining the agreement. There are no paid sick days under the tentative deal, Reuters notes. Unions asked for 15 paid sick days and the railroads settled on one personal day.

The tentative contract deal was proposed in September via a board appointed by the U.S. President Joe Biden. With this, the possibility of a year-end strike that could cause significant damage to the U.S. economy and strand vital shipments of food and fuel becomes imminent.

"We continue to urge both sides to finish their work in good faith and avoid even the threat of a shutdown," White House spokesperson Karine Jean-Pierre told reporters. "But like we do for all issues, our team is preparing and planning for all possible outcomes."

A rail traffic stoppage could freeze almost 30% of U.S. cargo shipments by weight, stoke inflation and cost the American economy as much as $2 billion per day by unleashing a cascade of transport woes affecting U.S. energy, agriculture, manufacturing, healthcare and retail sectors, according to Reuters.