London 2012: Transport for London staff strike
Customers could face difficulty accessing travel information as staff in Transport for London's call centres walk out in a dispute over bonuses for the Olympics.
A 24-hour strike was due to begin at 21:30 BST on Sunday, said the Rail, Maritime and Transport (RMT) union.
TfL said the action was "unjustified".
Tricia Riley, TfL's HR director, said: "We do not expect this to have a significant impact on the service we provide to our passengers."
The union said TfL had refused to meet at the conciliation service Acas to resolve the dispute.
RMT General Secretary Bob Crow said: "The rank hypocrisy of TfL managers, who stand to hit the bonus jackpot during the Olympics while offering their own directly employed staff nothing, stinks."