Train drivers on London Underground look set to take three days of strike action over a long-running dispute about pay and plans for an all night Tube service.
Leaders of the drivers' union Aslef will meet on Monday to decide whether to press ahead with stoppages which would cripple Tube services in the capital.
If the executive agrees, there will be a 24-hour strike from 21.14 on Wednesday January 27 followed by two further 24 hour strikes from the same time on February 15 and February 17.
LU has offered a four-year pay deal and said it will hire part-time drivers to staff an all-night service at weekends.
But unions have been seeking assurances for months about terms and conditions for their members.
Finn Brennan of Aslef said: "We genuinely regret the inconvenience that will be caused by any action but the behaviour of London Underground's senior management team have left us with no other choice.
"Our negotiating team last met London Underground at Acas on November 10 and since then they have refused to talk to us despite repeated requests.
"Our members have been extremely patient, they have waited for more than three and half years for promised talks on improving work life balance. There is still no indication when they will receive the pay rise that was due last April.
"We want to see an all-night service introduced, and we are not opposed to the recruitment of part time staff. But we will not accept a zero hours culture being introduced and working conditions undermined. Aslef wants a fair deal for existing staff and for new employees.
"We are ready to talk at any time to finally resolve this dispute. It is time for the mayor of London and his team at TfL to stop the political posturing and engage with us to stop London suffering more disruption."