The Communications Workers of America says negotiations in Philadelphia and New York stalled Saturday night after Verizon continued to demand more than 100 concessions from workers.
Verizon spokesman Rich Young says the company is negotiating "in good faith" to reach an agreement that "balances the needs of all parties."
The contract that expires midnight Saturday covers 45,000 workers, including 10,000 represented by the International Brotherhood of Electrical Workers.
CWA says the concessions are unjustified, given that Verizon is highly profitable - the company's revenue rose 2.8 percent to $27.5 billion in the second quarter. Its growth was largely attributed to its wireless business.