The Communications Workers of America union on Wednesday said about 17,000 workers in AT&T’s traditional wireline telephone and Internet business in Nevada and California who have been working without a contract for over a year would walk off the job on Friday afternoon for a three day strike if no deal is reached. On Tuesday, the union made a similar threat for 21,000 workers in AT&T’s wireless business spread across 36 states and Washington, D.C.

Workers are fed up with delays in the negotiations, Dennis Trainor, vice president of CWA District 1, said. “Now, AT&T is facing the possibility of closed stores for the first time ever,” Trainor said. “Our demands are clear and have been for months: fair contract or strike. It’s now in AT&T’s hands to stand with workers or at 3pm Eastern Time on Friday workers will be off the job and onto picket lines across the country.”

Get Data Sheet, Fortune’s technology newsletter.

AT&T said it was continuing to negotiate to reach a fair deal. “It’s baffling as to why union leadership would consider calling a strike when we’re offering terms in which their members, some of whom average from $115,000 to $148,000 in total compensation, will be better off financially,” a spokesman said. “We’re prepared for a possible strike. If it happens, we will continue working hard to serve our customers.”

Workers say they want larger wage increases, no increase in healthcare contributions, and tighter job security protection against outsourcing, among other issues. AT&T says it has offered “generous” wage and pension benefit increases and healthcare benefits similar to what other unionized employees have accepted around the country.

Tensions have been rising with the two groups of workers over the past year. The California and Nevada wired workers went out on a one-day grievance strike last month and have been holding large protest rallies. And earlier this month, some workers traveled to the Dominican Republic to meet with their counterparts there who now handle AT&T customer service calls and highlight the issue of jobs outsourced overseas.

The two contentious fights stand in stark contrast to the carrier’s long run of labor peace. AT&T hasn’t suffered a labor strike since 2012, and that lasted only two days. And a recent four-year contract ratified this month by 20,000 workers in Arkansas, Kansas, Missouri, Oklahoma, and Texas marked the 28th straight deal approved by AT&T and its unionized workers since the start of 2015. As part of the recent deal with workers in the South, AT&T agreed to hire 3,000 people locally for jobs that had been outsourced, mostly overseas.

But labor relations have been getting increasingly tense in the telecommunications industry since last year’s strike by Verizon (VZ) workers that resulted in higher pay and better job security than the company was initially offering.

AT&T (T), which is under pressure from Wall Street to cut costs amid slowing growth in its wired and wireless telephone operations, has previously said that it is not seeking to cut employee pay or take away benefits.