NEW YORK (AP) — Unionized UPS workers voted overwhelmingly on Friday to authorize a strike, setting the stage for a potential work stoppage if the package delivery company and Teamsters can’t come to an agreement before their contract expires next month.

The Teamsters said 97% of unionized workers voted for the authorization, which the union urged for in order to have more leverage during negotiations with the company. But a yes vote does not mean a strike is imminent.

“If this multibillion-dollar corporation fails to deliver on the contract that our hardworking members deserve, UPS will be striking itself," Teamsters General President Sean O’Brien said in a prepared statement. "The strongest leverage our members have is their labor and they are prepared to withhold it to ensure UPS acts accordingly.”

The Teamsters represent about 340,000 UPS employees, more than half of the company’s workforce in the largest private-sector contract in North America. If a strike occurs, it would be the first since a 15-day walkout by 185,000 workers crippled the company a quarter century ago.

UPS has grown vastly since then and become even more engrained in the U.S. economy. The company says it delivers the equivalent of about 6% of nation’s gross domestic product. That means a strike would carry with it potentially far-reaching implications for the economy.

UPS said in a prepared statement the strike vote does not impact the company's current business operations.

“Authorization votes and approvals are normal steps in labor union negotiations,” the company said. “We continue to make progress on key issues and remain confident that we will reach an agreement that provides wins for our employees, the Teamsters, our company and our customers.”

UPS workers are still seething about the current contract, which they feel was forced on them by prior union leadership in 2018 based on a technicality. The contract created two hierarchies of workers with different pay scales, hours and benefits. The union wants it eliminated.

In addition to addressing part-time pay and what workers say is excessive overtime, the union wants improvements to driver safety, particularly the lack of air conditioning in delivery trucks, which has been blamed for the death of a driver and hospitalizations of others.

On Tuesday, the union and the company announced they reached a tentative agreement to equip more trucks with air conditioning equipment. Under the agreement, UPS said it would add air conditioning to U.S. small delivery vehicles purchased after January 1, 2024.

But those changes aren’t extending to vehicles already in operation - at least not yet. Instead, the union says two fans would be installed in all vehicles when a new contract is ratified. It also said the company agreed to add heat shield to some vehicles, and put air vents in all cars within 18 months of a new contract. Under the agreement, UPS says roughly 95% of its existing U.S. package delivery fleet will be enhanced.

Teamsters spokesperson Kara Deniz said there have been two dozen tentative agreements reached with UPS since the negotiations began in April. The current contract expires on July 31.

UPS delivers around 25 million packages a day, representing about a quarter of all U.S. parcel volume, according to the global shipping and logistics firm Pitney Bowes. That’s about 10 million parcels more than it delivered each day in the years leading up to the pandemic.

UPS profits have soared since the pandemic began in 2020 as millions of Americans grew to rely on the delivery to their doorstops.

Annual profits at UPS in the past two years are close to three times what they were pre-pandemic. The Atlanta company returned about $8.6 billion to shareholders in the form of dividends and stock buybacks in 2022, and forecasts another $8.4 billion for shareholders this year.

The Teamsters say that profit growth is largely due to the hard work of UPS drivers and warehouse workers who carry everything from 50-pound bags of dog food and cases of wine to prescriptions.

The acrimony over the current contract was the impetus for workers rejecting a candidate to lead the Teamsters favored by longtime union head James Hoffa. Union members instead chose O’Brien, who has dug in on the Teamsters’ contract demands of UPS.

A win at UPS could also have implications for the organized labor outside the company.

There have been prominent labor organization campaigns at Apple, Starbucks, Trader Joe’s, Apple, even strippers at a dance club in Los Angeles. Teamsters are also attempting to organize workers at Amazon. On Friday, the new president of the United Auto Workers gave his strongest warning yet that the union is preparing for strikes against Detroit’s three automakers when contracts expire in September.