Talks to resolve the dispute behind the New Year's Eve Tube strike have broken down, said Transport for London.
The dispute is over new rotas
Informal talks between managers and the Rail, Maritime and Transport (RMT) union at Acas ended after four hours.
Unless the row over new rotas, linked to a 35-hour week is resolved, there will be another 24-hour walkout from Sunday evening.
London Underground called on the RMT to return to negotiations. The union wants mayor Ken Livingstone to intervene.
RMT general secretary Bob Crow said London Underground (LU) had refused its request to postpone the introduction of the new rotas from 5 February to 1 April.
Mr Crow said: "In order to avoid disruption, RMT requested that the new rosters, which leave many stations dangerously understaffed, be held off a couple of months while proper safety validations are carried out.
"Unfortunately, LU flatly rejected that offer underlining their complete intransigence which has already caused chaos for the travelling public."
The union says the new rotas will leave some stations dangerously understaffed, particularly in emergencies, and fears job cuts.
LU says there will be no job cuts and safety will not be affected. It said it went into Acas to discuss the issues, but the RMT had immediately threatened another strike.
It says suspending the new rotas, agreed by staff at 40 out of 44 station groups, would cause chaos, delay the 35-hour week, jeopardise holiday arrangements and deny benefits to "the vast majority of staff".
A spokesman said: "The RMT are well aware of the fact that the procedures for resolving outstanding issues are by no means exhausted.
"The RMT should return to the negotiations and resolve any issues they have by discussion. We remain committed to resolving this dispute at any time and with the least possible inconvenience to Londoners."
The row caused some disruption for Londoners on New Year's Eve, as thousands of RMT members walked out for 24 hours.
But Tube bosses and the mayor say there was less disruption than expected and many RMT members turned up for work - about 35 of the Tube stations closed on the night.
Now the union says some stations were kept open, despite insufficient staff - something denied by LU - and it is to ballot its Tube drivers and signal workers for go-slow action over the "safety breaches".
Mr Livingstone told BBC London he predicted several more strikes by the RMT who, he claimed, were left red-faced when the majority of members turned up for work on New Year's Eve.
"Rather than say they made a mistake, they will dig in and try to make the next strike more effective," he said.