The Teamsters working for shipping giant UPS said a strike is “imminent” after walking away from the bargaining table on Wednesday. 

The UPS Teamsters said in a statement late Wednesday that it has given UPS a one-week notice Tuesday to “act responsibly and exchange a stronger economic proposal” to more than 340,000 employees of the shipping company.

The Teamsters demanded that UPS deliver its “last, best and final offer” to the union by this Friday, June 30. 

Behind the headline: Teamsters strike with UPS could snarl commerce as labor flexes muscle

“The largest single-employer strike in American history now appears inevitable,” Teamsters General President Sean O’Brien said in a statement.

“Executives at UPS, some of whom get tens of millions of dollars a year, do not care about the hundreds of thousands of American workers who make this company run,” he said.

Earlier this month, UPS agreed to “equip all newly purchased U.S. small package delivery vehicles with air conditioning” in 2024.

The company also promised to install additional cab fans and heat shields in delivery trucks, after UPS came under fire for viral social media posts showing excessive temperatures putting drivers in uncomfortable and even dangerous working conditions.

But that momentum appears to have stalled.

The union has been vocal about how higher inflation and corporate profits have created an untenable situation for working class employees. O’Brien also took further aim at UPS management. 

“They don’t care about our members’ families. UPS doesn’t want to pay up,” O’Brien added. “Their actions and insults at the bargaining table have proven they are just another corporation that wants to keep all the money at the top. Working people who bust their asses every single day do not matter, not to UPS.” 

The UPS Teamsters have been engaged in ongoing negotiations for about two months, but a strike could thrust the commerce industry into chaos as it will lead to the largest U.S. strike in decades.

It will include over 340,000 warehousing, transportation and delivery workers bound by the largest private sector bargaining agreement in the country. 

The UPS Teamsters wrote that UPS risks “causing devastating disruptions to the supply chain in the U.S. and other parts of the world” with its Friday deadline.

They wrote that the Teamsters met with UPS negotiators late into Tuesday, but that they walked away from the table after they said UPS attempted to “withhold any additional benefits from the Teamsters, seeking concessionary language instead.” 

 “Time has run out for UPS to give workers that honorable contract,” Teamsters General Secretary-Treasurer Fred Zuckerman said in a statement. 

“The Teamsters repeatedly told the company from the beginning of this process that there would be no extensions,” Zuckerman said. “But UPS has sat on its hands and chosen to turn its back on these workers. Come August 1, it’s going to be damn hard for UPS to ignore us any longer.” 

The Hill has reached out to UPS for comment.