Plans to launch an all-night Tube service in London on September 12 have been deferred.

London Underground said it wanted to allow more time for talks with unions to reach a deal on pay and conditions for the new service.

No new date has been announced, but LU said it wanted an agreement to help launch the night Tubes in the autumn.

Rail unions have staged two 24-hour strikes in a dispute over the new service and had threatened longer walkouts this week before suspending the action.

London's Mayor Boris Johnson has said he "wasn't fussed" about a launch date, as long as night Tubes started in the autumn.

LU said practical arrangements were now in place, but talks with unions on rosters were continuing, so it was not possible to meet the September 12 date.

The company said it was "deferring" the launch to allow a successful conclusion of talks.

LU managing director Nick Brown 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 the 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."

Mick Whelan, general secretary of the drivers' union Aslef, said: "We welcome this decision by London Underground, which gives us all the time and space to negotiate properly on the introduction of the night Tube in the capital.

"Aslef believes that a world-class capital city like London needs a 24-hour Tube service, but not at the expense of the work-life balance of our members. It has to be done in a way that works for London Underground, for passengers, and also for the drivers who deliver this service every day.

"Had LU not acted in bad faith, by trying to introduce the night Tube in London without consultation, and without negotiation, we wouldn't be where we are today and they would have been in a position to deliver. Common sense has broken out at London Underground and now we can sit down with them and work this out."

David Leam, of business group London First, said: "This is disappointing for businesses, but if it gives London Underground and the unions time to come up with a long-term deal it will be worth it.

"It's high time we have a transport system that means London is truly a 24/7 city, as places like New York have been for years."

mfl Page 4: 10:29 Mr Johnson said: "The introduction of night Tube will be a hugely important moment for London and it's right that the positive discussions that are taking place with the unions should continue.

"As I've previously made clear, I'm not interested in a staring match over September 12 and I want to see night Tube introduced this autumn.

"Agreement on this is in everyone's interests - Londoners, businesses, visitors to our city and the hard-working London Underground staff who are central to making this happen.

"Further strike action isn't going to benefit anyone and I'd urge the unions' leadership to keep talking so we can get on and deliver night Tube for London."

The RMT has set two new dates of September 8 and 10 for more strikes if there is no agreement.

General secretary Mick Cash said: "RMT welcomes this move, which is what we have been calling for ever since we went into dispute over the night Tube issue.

"We warned repeatedly that it would be dangerous and foolish to press ahead with bodged night Tube plans until the very basics in terms of staffing and safety had been agreed with the unions through the long-established frameworks.

"This move proves that our members were right to strike and were right to warn the public about the consequences of the mad rush to introduce the mayor's night Tube plans without agreement.

"The fact that the plans have now been suspended indefinitely to some vague date 'in the autumn' is clearly a massive embarrassment to both Boris Johnson and George Osborne, but gives us an opportunity to now get the basics that should have been sorted months ago worked out through direct negotiation.

"In the meantime, our action scheduled for early September remains on."

Caroline Pidgeon, Liberal Democrat transport spokeswoman on the London Assembly, said: "This is a big climb down for the mayor.

"His retreat is entirely due to his error in setting a specific start date before all the staffing arrangements and other issues had been settled.

"By pushing for a set start date the mayor strengthened the union's negotiating position.

"The mayor must now also come clean and explain when the expected changes to night buses will take place."

Labour's London Assembly transport spokeswoman Val Shawcross, said: "With Boris Johnson's blundering approach to launching the night Tube, sadly this delay comes as little surprise.

"If you try and launch a major project without speaking to the people you'll be relying on to deliver it, it's never going to end well."