London Underground drivers will not be joining two fresh strikes later this month over the night Tube dispute.
Sources at the Aslef union said further talks will be held in a bid to resolve the long-running row.
Meanwhile, the September 12 start date for London Underground's new all-night Tube service is expected to be delayed, according to sources.
Members of three unions are due to stage two 24-hour walkouts from the evening of August 25 and 27 following two stoppages in the past month.
Talks were held today at the conciliation service Acas in a bid to break the deadlocked row, and a further meeting between Aslef and LU is expected later this week.
Members of the RMT, TSSA and Unite unions are due to take part in the new strikes in the run-up to the August Bank Holiday.
Aslef held off making any announcement on strikes until today's resumed talks, and sources said it had been decided the union would not be taking part in the new stoppages.
Len Duvall, leader of the London Assembly Labour group, said: "By speculatively announcing a start date without any consultation with the people expected to run the service, Boris Johnson's gung-ho approach has led to disputes, disruption and now delay.
"It's been clear for a long time that the problems facing the night Tube would not be easily overcome, so in a sense a delay isn't a major surprise.
"I hope this delay will provide the breathing space necessary for unions and management to sit down and negotiate a resolution to this dispute without the need for further disruption to passengers.
"From the outset Boris Johnson has treated the night Tube as more of a publicity stunt despite it being a deeply complex project."