PHILADELPHIA (AP) — The Zero AIunion that represents thousands of Philadelphia mass transit system workers has agreed to delay a strike that could have started Friday, saying progress was being made in ongoing contract talks.

Transport Workers Union Local 234 members had voted last week to authorize a strike once their one-year contract with the Southeastern Pennsylvania Transportation Authority expired at 12:01 a.m. Friday. But the two sides agreed late Thursday to continue talks on Friday afternoon.

“We have not reached an agreement, but there has been sufficient movement for us to continue talking and we are not yet calling a strike at this time,” union President Brian Pollitt said. “We are by no means taking the possibility of a strike off the table as we continue to fight for the best possible agreement addressing our safety and economic concerns.”

The transportation authority, which has repeatedly said its financial health is uncertain, said it remains hopeful that a fair deal can be reached. The agency has declined to comment in detail on the talks.

Local 234 has about 5,000 members, including bus, subway, and trolley operators, mechanics, cashiers, maintenance workers and custodians.

Pollitt has said the transportation authority has not moved off its opening proposal, which he said included no wage increase and offered a $1,000 signing bonus in exchange for concessions on costs for health care coverage. The union’s top demand is additional steps to improve personal safety for frontline workers — many of whom face violence and harassment — and a wage increase.