Last ditch talks aimed at averting strikes by London Underground workers in a row over ticket office closures, will be held tomorrow, with time running out for a deal to be agreed.
Members of the Rail, Maritime and Transport union (RMT) and the Transport Salaried Staffs Association are due to walk out for 48 hours from 9pm on Tuesday, and again a week later in protest at the closures, and the loss of hundreds of jobs.
London Mayor Boris Johnson has offered to hold talks, but only if the industrial action is called off.
The two sides met at the conciliation service Acas last week, with little sign of a breakthrough.
Bob Crow, general secretary of the RMT, said: "The Acas talks reconvene tomorrow and RMT remains totally committed to making progress through those negotiations.
"In the meantime I have had further correspondence with Boris Johnson and we are available for direct talks with the Mayor with no preconditions.
"We are awaiting his confirmation that be is up for getting round the table with no preconditions or caveats."
London Underground has announced contingency plans for the strike days, but passengers face travel chaos if the action goes ahead.
Transport for London tonight repeated its warning that Tube services will be hit if the strikes go ahead as planned.
In a statement, it said: "Should the RMT and TSSA strike action go ahead, London Underground will keep as many stations open and run as many trains as possible.
"Services will be affected from 9.30pm on Tuesday February 4 so customers are asked to try to complete journeys as early as possible that evening.
"If your Oyster card needs topping up, it may help to do this in advance of the industrial action starting.
"There will be disruption to journeys on Wednesday and Thursday, when Tube services will start later and finish earlier than normal - trains will run from around 7am to 11pm."
London Underground managing director Mike Brown said: "My message to the union leaderships is that it's not too late to do the right thing, call off this completely unnecessary strike and work with us to help shape the future of the Tube. All a strike will achieve is to lose those who take part four days' pay.
"Should the strike go ahead, we'll do all we can to keep customers informed and ensure we keep London moving and open for business."