Sadiq Khan has refused to rule out freezing fares if he wins a second term as London mayor in next year's election.
Khan was asked by the London Assembly transport committee chair Caroline Pidgeon whether he would look at freezing fares again if he was re-elected as mayor.
Khan replied: "You'll have to watch this space. I'm not going to reveal my manifesto now, as tempting as it may be. I'm more confident now than I was before I became mayor of making public transport affordable for Londoners."
The London mayor announced a partial fares freeze in his 2016 election manifesto. Bus and tram tickets, pay as you go journeys on the Tube, DLR and TfL rail services have all been frozen until 2020. The freeze has not applied to travelcards, monthly Oyster cards or daily caps.
However, Khan has come under pressure to drop the policy because of the £640m hole it has left in Transport for London's (TfL) budget.
TfL is already struggling under the financial strain of the Crossrail delay, a subdued economy and a £700m loss from central government funding.
Last year TfL admitted its fare income will be £2.1bn lower than expected for 2019-20 to 2023-24, while the delayed opening to the Elizabeth Line will cost TfL £600m alone in lost revenue over the next five years.
In 2020 Khan will be up against Shaun Bailey, the Tory candidate for mayor. Other candidates in the race include the Lib Dems' Siobhan Benita and the Green party's Sian Berry.
City A.M. reported in November that Bailey will stand in the London Assembly's 2020 elections despite his bid to take on Khan for the top job at City Hall.