SBC Communications, one of the biggest US phone companies, is planning to cut more than 10,000 jobs, or about 6% of its workforce, by the end of next year.
SBC workers went on strike earlier this year
Phone companies want to reduce costs as demand wanes for fixed-line services and legislation outlaws services such as "cold-call" selling.
SBC has shed 7,000 jobs this year and analysts say it may need to trim as many as 20,000 to catch up with rivals.
Staff went on strike earlier this year as they wrangled over new contracts.
SBC said that most of the losses would come through attrition, when people either retire or leave the firm, and it will guarantee job offers made to union members in the new contracts.
"This has been an ongoing process, and has been for the past three or four years," said SBC spokesman Walt Sharp.
Lehman Brothers analyst Blake Bath said that cutting 10,000 to 20,000 jobs will save SBC between $600m and $1.2bn a year.
SBC has 165,000 workers.