Millions of commuters are pinning their hopes on peace talks today to avoid a repeat of last week's misery caused by a 48-hour tube strike.
Members of the RMT and TSSA unions are due to stop work at 9pm tomorrow in their second strike over ticket office closures.
London Underground managers held talks with union officials at the conciliation service ACAS on Friday.
Both sides agreed to meet again today in the hope of reaching an agreement in time to call off tomorrow's action. - but the clock is ticking.
RMT General Secretary Bob Crow insisted on Friday the strike was still on, despite the negotiations.
Any peace deal will first have to be approved by the RMT's executive council before the strike can be suspended.
Last week's shutdown saw widespread disruption on Tuesday night and throughout Wednesday and Thursday.
London Underground said it was able to run trains on nine out eleven lines but services were patchy.
Many commuters were forced onto overcrowded mainline commuter trains and buses.