The clock is ticking for tens of thousands of wireline workers at AT&T Inc. Come this weekend, their contracts expire.

If the union representing the workers is unable to reach an accord with Dallas-based AT&T on new contracts, AT&T might have to brace itself for another massive strike following the one last year by Verizon workers.

Contracts covering around 40,000 workers at AT&T East, Midwest, West and Legacy expire at midnight on April 7, according to the Communications Workers of America.

Members of the CWA at four AT&T units recently voted to authorize leaders of the union to call strikes if the negotiations come up short.

AT&T has been negotiating with the union on benefits, pension, wages and work rules covering employees with call center and network positions, AT&T spokesman Marty Richter said.

“As one of the largest employers in America, we’re proud of the number of high-paying, middle class careers we’ve produced,” Richter said in an email. “Our goal is to do everything in our power to protect those careers.”

Richter said AT&T is not proposing to reduce workers’ wages or rescind healthcare benefits. He said the average network technician covered under the current contracts earns $133,000 in benefits and wages while the average call center rep makes $107,000.

On a website dedicated to the negotiations, AT&T said on March 22 that it and the CWA have exchanged dozens of proposals in the negotiations. Healthcare is one of the areas where AT&T and the union have gone back and forth with different proposals.

“Core wireline CWA employees currently pay about 60 percent less for health care than union employees in other areas of our business, AT&T managers, and the national average,” AT&T asserts on the website.

A spokeswoman for the CWA did not return a phone call placed Tuesday seeking comment on the negotiations.

A strike by AT&T workers would represent the second major strike of a U.S. telecommunications company over the last several months.

In one of the biggest walkouts in recent times, around 45,000 Verizon workers last year went on strike after the unions representing them were unable to come to an agreement with the telecom titan on a new contract.

The workers returned to their jobs in August but still have been unable to reach a new accord with Verizon. The workers have been operating under an expired agreement; a spokesman for Verizon didn’t immediately respond Tuesday to a request for confirmation that the workers continue to be protected under the old contract.