Talks aimed at averting more strikes by London Underground workers in a row over job cuts ended without agreement today.
The Transport Salaried Staffs Association (TSSA) said another 24-hour Tube strike was likely to go ahead from October 3, with further walkouts planned for November.
TSSA and the Rail Maritime and Transport union (RMT) said insufficient progress had been made at today's talks with Transport for London to call off the industrial action.
The unions said they put a series of proposals to management to try to save 800 jobs threatened with the axe.
TSSA said its leaders will be away next week at the Labour Party conference in Manchester, adding that a deal looked "unlikely" before the next planned walkout.
Manuel Cortes, TSSA deputy leader, said: "We have had a day of hard bargaining but as things stand tonight, the next strike is still on.
"We hope to hear something positive from LU by Friday - the ball is now firmly in their court."
RMT leader Bob Crow said: "We set out proposals in line with our objectives of protecting safe staffing levels and we await a formal response."
An Acas spokesman said: "Talks between London Underground, TSSA and RMT, which took place today at conciliation service Acas, have now been adjourned. The parties have gone away to reflect on their positions and we remain in close contact with them."