Commuters will not be told whether Tuesday's planned Tube strike will go ahead until late on Monday.
Three of the four unions have decided to call off the 24-hour walkout after receiving an improved offer in the dispute over night tube services and annual pay.
London Underground has offered a four-year pay deal and said it will hire part-time drivers to staff all-night services at the weekends.
A last-minute meeting is to be held by the RMT union on Monday.
The RMT is the largest of the Tube unions, with members including station staff, some train drivers, and engineers.
If the strike goes ahead, RMT workers will work out from 6.30pm tomorrow evening.
Transport for London (TfL) is planning an emergency service should the strike go ahead. It says travel advice and updates for passengers will be issued "as soon as possible".
TfL will inform passengers of the decision through station posters, loud speaker announcements and social media.
Two further strikes are planned for Monday 15 February and Wednesday 16 February.
