Citing changes to health plans that would force UPS employees to shoulder more expense, unions in Philadelphia, Western Pennsylvania and Louisville, Ky., have refused to accept separate contracts covering workplace rules, wages and benefits.

UPS said it continues to make progress with the Teamsters and expects to resolve the issue.

“It remains business as usual,” UPS spokesman Dan McMackin said in an email. “We remain confident that the local contracts will be finalized.”

Everyone hopes to avoid shutting down a facility because of a walkout, said Gary Piso, UPS alternate steward of Teamsters Local 249, but that option remains if UPS refuses to continue health benefits at the current level.

“Nobody wants a strike,” Piso said. “If it’s necessary, there are a lot of people willing to go that route. That’s the one muscle we have.”

The situation has not affected operations, though it delayed wage increases for employees. Until a five-year agreement goes into effect, UPS employees are covered under the old contract, which was extended indefinitely upon its July 31 expiration.

A national master contract covering 240,000 full- and part-time UPS employees was approved in June. But before that can take effect, union members must approve region-specific supplemental contracts.

They have approved all but three of the 28 supplements. Ohio union members approved their supplemental agreement on Wednesday, but the contracts covering nearly 12,000 workers in Western Pennsylvania, Philadelphia and Louisville remain unapproved.

Louisville is an air-shipping hub for the company and critical to UPS operations. Ballots were mailed to the 7,000 union employees, and the vote will be counted on April 10, said Fred Zuckerman, president of Louisville Local 89.

Nearly 90 percent of Louisville union members rejected the contract in October, and Zuckerman said they probably would defeat it again.

“It’s going to go down big,” he said. “Everybody knows it.”

The holdout caused some tension between local unions and the International Brotherhood of Teamsters.

The national organization wants the Pennsylvania and Louisville workers to sign off on the contracts, saying that UPS employees still would enjoy better benefits than most Americans.

“This is excellent health care coverage,” said Leigh Strope, an international Teamsters spokeswoman. “At a time when most Americans are worried about health care, this provides certainty.”