Union officials and Tube bosses will meet later today for talks in an attempt to avert another strike by resolving a dispute over plans to close all Tube ticket offices and cut jobs.
The Underground network was disrupted for 48 hours when members of the Rail, Maritime and Transport (RMT) union walked out on Monday night.
The union is planning to strike for another 48 hours from 9pm on Monday.
Negotiations between the RMT and London Underground (LU) are scheduled at the conciliation service Acas.
Transport for London (TfL) has said its proposals to close all Underground ticket offices, which would lead to up to 960 job losses, would save £50m a year.
The RMT is calling for London Underground to hold a public consultation on the plans.