The launch of the 24-hour London Underground (LU) service has been postponed.
The all-night tube service, set to run on selected Friday and Saturday evenings, was due to start on 12 September.
No new commencement date has been announced.
According to Politics Home, LU's managing director Nick Brown said the organisation was close to reaching an agreement on pay and conditions.
He said: "Further to the progress made in recent days with the trade unions and the suspension of strike action, we believe we are not far from an agreement that protects the work-life balance of our employees and is affordable, sustainable and fair.
"As such, we have decided to defer the introduction of Night Tube to allow more time for those talks to conclude. Our objective is to reach an agreement that ends this dispute and delivers the Night Tube for Londoners this Autumn.”
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Workers had been set to stage two two-day strikes this week but they were called off at the last minute as a “goodwill” gesture, according to Unite.
Dame Tessa Jowell responded to the news on Twitter:
Boris refusal to engage w staff at appropriate time means Londoners forced to wait for 24-hr Tube - not good enough https://t.co/3GKo1Fv2Ek— Tessa Jowell (@TessaJowell) August 27, 2015
Jowell is campaigning to become Labour's candidate for the mayoral election in 2016.
A number of strikes over the summer crippled the capital.
In July, unions staged their biggest walkout in 13 years over the introduction of the night tube.
The Rail, Maritime and Transport union (RMT) described the service as a "vanity project" of Mayor Boris Johnson, claiming it was "fundamentally flawed from top to bottom".