S-B-C Communications says it´s taking steps to head off service problems during a four-day nationwide strike set to begin just after midnight.
Thirty-thousand phone workers in California and Nevada are expected to join the walkout.
During the strike, the company says routine calls for directory assistance will be answered by S-B-C retirees and replacement workers.
Many other operations, including call switching and S-B-C-Yahoo high-speed Internet service, are automated and may not be affected by the strike.
Calls for installation or repairs may be delayed, but S-B-C says it has hundreds of managers and temporary workers ready to handle such calls.
The four-day strike has been called a bargaining tactic in the union´s ongoing contract talks.