Jon Lamonte of Tube Lines says they have prepared contingency plans to keep the Underground moving during the strike. Some maintenance workers will walk out at 4pm this afternoon.
Maintenance staff on three tube lines are entering their third day of strikes today.
A strike affecting the Jubilee, Northern and Piccadilly lines goes ahead from 4pm.
Union bosses have forecast "widespread" disruption, as workers who maintain and upgrade tube lines go on strike next week.