CHICAGO (Reuters) - Air maintenance workers at United Parcel Service Inc UPS.N have voted overwhelmingly to authorize a strike against the world's largest package delivery company as contract talks remained deadlocked over health-care benefits, the workers' union said on Monday.

United Parcel Service aircraft are loaded with package containers at the UPS Worldport All Points International Hub in Louisville, Kentucky, U.S. December 17, 2013. REUTERS/John Sommers II/File Photo

Teamsters Local 2727 said 98 percent of those who took part in a mail-in ballot voted to authorize strike action. Eighty percent of the local’s 1,200 members participated in the ballot.

Contract talks have been ongoing for three years. If they remain deadlocked Monday, union representatives say they will begin the process that could lead to a strike within 60 days.

The main sticking point has been healthcare benefits. The Teamsters say UPS is demanding major concessions, including a massive spike in retiree contributions for health-care costs.

“UPS wants huge concessions and our members are not willing to take them,” Local 2727 President Tim Boyle said. “We’re not asking for anything we don’t already have and this demonstrates our members are willing to strike.”The air maintenance staff work at hubs around the United States, with more than one-third in Louisville, Kentucky, which is UPS’ main hub.

“UPS continues to negotiate in good faith for a contract that is good for our employees, our customers and our company,” a UPS spokesman said. “We are confident talks will be completed successfully.”

The company said it was also hopeful that contract talks can be concluded “without any disruption” to customers.

A strike could ground UPS’ airplanes, affecting packages shipped by air. While it would not halt all deliveries, it would be a major disruption.

The air maintenance workers are governed by the U.S. Railway Labor Act, which only permits strikes after negotiations and mediation have failed.

If talks remain deadlocked Monday, the Teamsters say they will ask the federal mediator overseeing negotiations to release the union from the bargaining table. If there is no resolution after a 30-day cooling-off period, a board appointed by the president would have to rule on a strike, which would take up to 30 days.

A strike would be highly unlikely during UPS’ crucial holiday peak season this year. But it could go before the presidential board before President Barack Obama leaves office in January.

Kevin Gawlik, an air mechanic for 20 years who works at a UPS air hub in Rockford, Illinois, voted to strike. He said the work is tough and can result in health problems, including hearing loss from working around jet engines.

“That’s why I’m willing to walk out and strike to keep my benefits,” Gawlik, 49, said.

In trading on the New York Stock Exchange, UPS shares were down 0.3 percent at $113.94.