Unionized UPS workers have voted to authorize a strike as contract negotiations continue, paving the way for a possible work stoppage as soon as August 1.

After more than a week of voting, about 97% of UPS workers who cast ballots voted in favour of the industrial action.

UPS acknowledged the strike authorization outcome but said that such action wouldn't automatically trigger a work stoppage at the country's largest carrier.

"The International Brotherhood of Teamsters announced it received approval from its UPS members, who voted on its strike authorization," UPS said in a statement Friday.

"The results do not mean a strike is imminent and do not impact our current business operations in any way," it added, noting that authorization votes and approvals are normal steps in labour union negotiations.

"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 said.

The announcement of strike authorization comes more than a week after UPS also reached a tentative deal on heat safety that would cover 340,000 delivery drivers and package handlers.