After the Teamsters Union, which represents United Parcel Service (UPS:US) workers, said the delivery business “walked away” from negotiations over a new contract, shares in the company fell in early Wednesday trading.

“Around 4AM, UPS walked away from the bargaining table after presenting an unacceptable offer to the Teamsters that did not address members’ needs. The UPS Teamsters Nat’l Negotiating Committee unanimously rejected the package,” the union said in a tweet.

The shipping giant denied these claims, accusing the union of stopping “negotiating despite UPS’s historic offer that builds on our industry-leading pay.”

Teamsters insists that it’s up to UPS to make “a last, best, and final offer.”

“This multibillion-dollar corporation has plenty to give American workers — they just don’t want to,” said Teamsters General President Sean M. O’Brien. “UPS had a choice to make, and they have clearly chosen to go down the wrong road.”

Investors are growing increasingly concerned about the prolonged negotiations between the union and UPS as the current contract is set to expire on July 31. Teamsters authorized a strike in case talks break down despite both sides saying earlier that they are committed to a deal.

The company added that the union’s refusal to negotiate “creates significant unease among employees and customers and threatens to disrupt the U.S. economy.”

UPS shares fell 2% on Wednesday after rising to its highest levels in 2 months. Several Lawmakers were selling the stock recently, including Ro Khanna, Josh Gottheimer, Shelley Moore Capito, and Scott Franklin.