An estimated 17,000 AT&T employees in California and Nevada went on strike Wednesday to protest what they claim is the illegal way in which the company is handling work assignments for technicians. The walkout underscored nearly a year’s worth of simmering workplace tensions at the telecommunications company.

Relations have been fraying between AT&T and Communications Workers of America District 9, the union representing the workers, since their contract expired nearly a year ago. The two sides have been locked in protracted negotiations trying to hammer out a new agreement. Employees at the company’s retail stores are not covered by the contract and did not participate in the strike.

The workers — 98 percent of whom are in California — moved to strike over what they claim is AT&T’s practice of directing lower-salaried workers to perform jobs that their contract reserves for their more experienced, higher-paid colleagues. Up to 2,968 workers in the Bay Area were expected to participate in the walkout, according to a union spokeswoman.

The workers claim that allocating work in such a way threatens the positions of employees with more seniority, and fails to compensate less experienced technicians for working above their pay grade. The CWA also plans to file a complaint with the National Labor Relations Board, the federal agency that enforces labor law.

“It’s about respect,” said Orange Richardson IV, a maintenance splicing technician in San Francisco who’s been with AT&T for 20 years.

“We don’t mind if you want to train our workforce to make them more educated and successful, but you should also compensate them for it,” said Richardson, who also serves as president of the CWA’s San Francisco office.

“You have to take a stand at some point. You can’t be disrespected every day.”

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The union said its workers will remain on strike until they reach an accord with AT&T. The work assignment dispute that prompted the strike Wednesday could be resolved before a full contract is agreed upon.

The union has also repeatedly called on AT&T to end its practice of sending call center and customer support jobs overseas as the contract negotiations have dragged on. It upped the pressure on the company last week, presenting a letter signed by dozens of elected officials in California and Nevada that pledged support for the workers and slammed the company for failing to provide access to quality communications services, particularly in rural areas, while maintaining high levels of executive pay.

About two dozen AT&T employees protested outside the main administrative office on Bush Street in San Francisco, holding placards and calling for a fair contract.

“We want the company to come back to the table, to bargain in good faith and give them the fair share for their job title,” said Jacque Coniglio, an AT&T call center worker and union steward who helped lead the San Francisco picket line.

AT&T spokesman Steven Maviglio said that while he couldn't comment on the specifics of labor negotiations, “We’re addressing this grievance, and we think what we’re offering is extremely reasonable.”

“We don’t think it’s in anybody’s best interest, and it’s unfortunate that the union chose to (strike), but we’re in continual discussions and we hope to get everybody back to work as soon as possible,” Maviglio said.

“We have thousands of unionized employees in the state, and we’re familiar and compliant with the law and the terms of our bargaining agreements.”

Dominic Fracassa is a San Francisco Chronicle staff writer. Email: dfracassa@sfchronicle.com Twitter: @dominicfracassa