Talks aimed at averting threatened Tube strikes on New Year's Eve have been adjourned until Friday after last-ditch negotiations.
Signal workers are in dispute over possible job cuts
The deadline had been moved from 3pm to 4pm in an effort to reach a deal.
Two 24-hour strikes are expected to go ahead on New Year's Eve and 4 January over signalling staff's conditions.
The Rail Maritime and Transport (RMT) union's talks with London Underground (LU) would continue after Thursday's talks ended without agreement.
"We have made it abundantly clear that longer shifts, shorter minimum rest breaks and the loss of jobs are simply not acceptable," said general secretary Bob Crow.
"Our members have made it absolutely clear that after four years waiting for London Underground to sort out this mess they have finally run out of patience," he said.
LU's chief operating officer Mike Brown said: "A strike on New Year's Eve would be a great disservice to the capital and those wishing to travel during the holiday celebrations.
"We have been talking to all the trade unions and we are willing to talk as long as it takes to resolve these issues."
The threatened strikes have brought criticism from both shadow transport secretary Tim Yeo and Liberal Democrat London Assembly Transport spokeswoman Lynne Featherstone.
PLANNED 24-HOUR TUBE STRIKES
0001GMT, 24 December - Piccadilly Line
1200GMT, 31 December - Whole network
2100GMT, 3 January - Whole network
0001GMT, 5 January - Piccadilly Line
Meanwhile, Piccadilly Line drivers will strike on Christmas Eve and 5 January.
RMT members voted by 186 to 13 (93%) to back industrial action.
General Secretary of the union Bob Crow said he expected a complete shut down of Tube services.
The strikes are set to cripple Tube services on New Year's Eve when thousands of revellers are likely to be in central London to see in 2005.
They will start at 1200GMT on New Year's Eve and 2100GMT on 3 January. Both will run for 24 hours.
Aslef members on the Piccadilly Line are staging their two 24-hour walkouts starting at midnight in protest over a colleague's demotion for passing through four red signals.
LU has advised passengers travelling on Friday to seek alternative routes and leave extra time for their journey.
Extra bus services will be laid on but London Underground warned there will be delays.
A Tube service to Heathrow airport will run every eight minutes.