The RMT has ended talks aimed at averting a strike planned for Sunday by London Underground workers.
A 24-hour walk-out now looks set to go ahead across underground networks in the capital from 6pm.
While a second union is still meeting London Underground to discuss a dispute over jobs and ticket office closures, RMT, the biggest rail union, has walked away.
Officials from RMT and the Transport Salaried Staffs Association had met with LU under the chairmanship of the conciliation service Acas for a fourth day of talks.
But the RMT left the meeting without any sign of progress being made.
TSSA general secretary Manuel Cortes remained at Acas, making it clear he was determined to continue trying to break the deadlock.
Damon Smith, 19, has been charged with making or possessing an explosive substance with intent to endanger life.Read the full story ›
London's Night Tube began on Friday with Sadiq Khan on board the first departure.Read the full story ›
London's Night Tube began on Friday with Sadiq Khan on board the first departure.
Roughly 50,000 people are expected to use the Night Tube service each weekend, with the number growing to 200,000 by the Autumn when the service extends to the Northern, Jubilee and Piccadilly lines.
The mayor chatted to passengers on the historic evening, telling one: "You're making history".
The long-awaited Night Tube will finally begin this weekend - almost three years since the plan was first announced.Read the full story ›
Phil Sayer, whose voice was heard on most automated PA systems on railway stations across the UK, died from cancer on Thursday.Read the full story ›
Talks aimed at breaking the deadlock over plans for an all-night Tube service in London are set to resume today.
Rail union leaders will meet London Underground bosses under the chairmanship of Acas, the conciliation service, for a fresh attempt to reach an agreement on pay and conditions.
The night Tube was originally planned to start in September but as negotiations dragged on it has been delayed, with no new date for its launch.
London mayor Boris Johnson cast fresh doubt over the planned service last week when he said it was not "absolutely critical".
The London Underground and Rail, Maritime and Transport are holding last-ditch talks just hours before a three day strike, that could affect millions of people across London and surrounding areas.
Conciliation service Acas said the talks between the RMT and London Underground started at 10am.
RMT union members are set to walk out of their jobs for three days at 9pm this evening, in a long-running dispute with the London Underground over ticket office closures.
A two-day strike last week caused huge disruption, with roads clogged as people switched to other forms of transport.
Old Routemaster buses were in operation around the capital today as Transport for London attempted to keep London moving during the Tube strike.
TfL said there was a record number of buses on the capital's roads after 266 extra buses were brought in for the first day of the 48-hour walkout.
David Cameron described travel disruption caused by the Underground strike in the capital as "unacceptable" on Twitter.
It's unacceptable that millions of people are having their lives disrupted by today's Tube strike in London.