Last-minute crisis talks are being held today to avoid a 24-hour strike that would cause havoc for commuters on Monday. The members of the Transport Salaried Staffs Association (TSSA) and the Rail, Maritime and Transport (RMT) are meeting again in the hope an agreement can be reached at the conciliation service Acas.
Earlier negotiations failed to come to a deal to sort out the staffing and safety crisis caused by the slashing of nearly 900 station jobs.
The strike, if it goes ahead from 6pm on Sunday and Monday (January 8 and 9), will see almost all zone stations closed and a "severely reduced service" on the rest of the network.
Piccadilly line services will still run between Hammersmith and Heathrow Terminals 1, 2 and 3, but there will be no service to Terminals 4 or 5.
The Mayor of London, Sadiq Khan, urged unions to "call the strike off immediately".
He said: "I have instructed TfL to work around the clock throughout the weekend to continue negotiating to resolve this dispute. There is no reason for the unions to strike.
"I can assure Londoners that we will continue to do everything we can to avert this strike."
Steve Griffiths, chief operating officer for London Underground, said: "There is no need to strike. We had always intended to review staffing levels and have had constructive discussions with the unions.
"We agree that we need more staff in our stations and have already started to recruit 150 extra staff. This number is bound to increase as we work through the other areas that need to be addressed. Taking into account existing vacancies and natural turnover this means that around 500 staff will be recruited for stations this year. There will also be increased opportunities for promotion.
"All of this will ensure that our customers feel safe, fully supported and able to access the right assistance in our stations at all times. We encourage the unions to continue working with us on this process and we are available for talks at all times through the weekend in order to resolve this dispute."
Manuel Cortes, the TSSA general secretary, said: "We are extremely disappointed not to have a solution to the dispute this evening but we have just been asked to return to talks with LU under the auspices of Acas (on Saturday) morning. We will be attending and look forward to hearing what they are offering."