A strike by members of the Communications Workers of America could affect local phone service in SBC's 13-state coverage area, which includes Illinois.
But in Illinois, most of SBC's unionized workers are represented by the International Brotherhood of Electrical Workers, not the Communications Workers union.
SBC's contract with the IBEW doesn't expire until late June, but union spokesman Tom Hopper says some members of the Electrical Workers union may be reluctant to cross picket lines set up by striking workers.
SBC has said is has contingency plans for management employees and retirees to handle key duties in case of a walkout.
Any strike will be SBC's first since 1983.