The two sides in the bitter tube dispute were refusing to give ground as the latest round of peace talks got underway.
London Underground managers met officials from the RMT, Aslef, TSSA and Unite at the conciliation service ACAS in Euston.
Members of the biggest union, the RMT, are due to begin a three-day strike on Monday.
The RMT said it was sticking to its demand for the withdrawal of the ticket office closures.
RMT negotiator John Leach said the union also wanted a public consultation.
"We're putting the same case that we put last time because what we're saying is reasonable.
"If they can suspend the implementation of the booking office closures and the job cuts and the people can have a full and proper consultation, staff issues can be addressed, then we can suspend the strike.
"The ball is in management's court."
London Underground Chief Operating Officer Phil Hufton said there would be no more changes to the proposal to close 254 ticket offices and axe 950 jobs.
"We can't keep hanging around, we've got a job to do. We've got to modernise the tube and we've got to become more efficient.
"We've made significant changes to our proposals.
"The ball is now firmly in the RMT leadership's court."