The walkout, over a long-running jobs dispute as TfL pushes ahead with ticket office closures, is due to start at 9pm this Saturday and will continue until the same time on Monday evening.
It is separate to the Night Tube strikes, which have currently been called off.
Steve Griffiths, chief operating officer for London Underground, went further, saying in a statement: "The only thing a strike will do is badly hit hardworking Londoners and lose staff two days' pay and a £500 bonus".
That £500 is linked to the pay deal staff have been offered on the pay and Night Tube dispute.
Griffiths added: “Ticket offices that customers were using in ever dwindling numbers have already closed with more staff than ever now moved into ticket halls, gate lines and platforms where they can help customers more effectively. As a result, we are seeing big increases in customer satisfaction, particularly in the helpfulness of staff.
"We have delivered every commitment we made to our staff – there have been no compulsory redundancies, work life balance has been protected and there’s a job for anyone with no loss of pay. Around 900 station staff will be promoted or move from fixed-term contracts to permanent roles. There is clearly absolutely no basis whatsoever for this strike threat.”
A TfL spokesman told City A.M. the action was "absurd", given that the process for closing station ticket offices has already begun.
Talks are taking place at TfL's offices between the two sides today to see if a compromise can be reached.