Nearly 21,000 union wireless workers have put AT&T on notice, canceling their temporary contract with the carrier and warning of the possibility for a strike as long-term contract negotiations drag on.

An AT&T spokesman on Friday said the carrier “continue(s) to bargain with the union and remain(s) confident a fair agreement can be reached.”

“We value all of our employees, and we’re committed to reaching fair labor agreements that allow us to continue to provide good-paying U.S. union jobs with excellent benefits,” the carrier said in a statement.

The announcement from Communications Workers of America members comes nearly two and a half months after the employees’ previous contract with AT&T expired on February 11. The retail, call center, and technical workers, who are spread across 36 states, that month approved the use of strike tactics in the event that negotiations with AT&T failed.

AT&T and the unions agreed to a temporary contract extension in February, but that came with the caveat that the contract could be terminated with 72 hours’ notice. At the time, CWA said workers would continue to bargain with AT&T with the expectation that the carrier would “come to the table with good faith proposals.” The workers said they were looking for a “fair contract that ends offshoring and outsourcing and supports high quality customer service.”

It seems, however, that CWA workers are sick of waiting.

“We have given AT&T every opportunity to show their commitment to finding common ground and a fair contract and, quite frankly, have been very patient about it. But time is running out for AT&T to stop undermining good jobs, quality customer service, and its long-term success,” Dennis Trainor, vice president of CWA District 1, commented. “AT&T thinks they can play by their own rules, but 21,000 wireless workers are ready to show them what happens when you bet against American workers.”

The move is clearly meant to put pressure on AT&T as CWA pushes for more favorable contract terms for employees. Last year, nearly 40,000 Verizon workers walked off the job after contract negotiations stalled, resulting in a 49-day strike that was resolved only when the U.S. Labor Secretary intervened to bring both parties back to the bargaining table. The seven-week strike impacted Verizon’s second quarter earnings, dragging down total operating revenue and earnings per share.

While this spat has yet to be resolved, AT&T has been successful in negotiating a number of other union contracts in the past several months. Just this week, the carrier struck a five-year labor deal covering around 5,000 members of the International Brotherhood of Electrical Workers. That contract was negotiated ahead of the previous agreement’s June 24 expiration date and included a 13.25 percent wage increase, a $1,000 signing bonus, a bump in pension benefits, and a no-layoff clause that will run through March 1 of next year.