The Teamsters, in June, said roughly 97% of its UPS members had authorized a strike. The current agreement is set to expire on July 31, but the union had set a July 5 deadline, saying it needed the remaining days to ensure members would have sufficient time to review it and vote on it.

Negotiations reportedly ran until 4:00 a.m.—and both sides are already pointing fingers at the other for the breakdown in talks.

“UPS walked away from the bargaining table after presenting an unacceptable offer to the Teamsters that did not address members’ needs,” the union wrote in a release. “The UPS Teamsters National Negotiating Committee unanimously rejected the package.”

The company, though, said that wasn’t true.

“The Teamsters have stopped negotiating despite historic proposals that build on our industry-leading pay,” UPS countered. “We have nearly a month left to negotiate. We have not walked away, and the union has a responsibility to remain at the table.”

UPS and the union have already agreed to a tentative increase in salaries, air conditioning in trucks, and doing away with the two-tier driver system, which paid weekday workers more than drivers who work on weekends.

The stalemate has raised fears that the company, which handles 24% of Amazon’s deliveries, could see another work stoppage, like the 15-day walkout in 1997 that crippled the company.

The two parties last agreed on a contract in 2018, when another strike was threatened.

Today, UPS is an even larger company that is more integral to the economy, given the rise of online shopping. It has estimated it delivers roughly 6% of the nation’s gross domestic product. That has resulted in a big boost to its profits. Last year, UPS delivered about $8.6 billion in returns to shareholders, in the form of dividends and stock buybacks.

The Teamsters say they will not work past the expiration of the current contract. And “no additional negotiations are scheduled.”