The opening date for the long-awaited Sydney Metro City rail service has been delayed, just days before commuters were due to hop on board.
The Office of National Rail Safety Regulator confirmed to 7NEWS it had not signed off on the safety checks required for the metro to begin operating as planned on August 4.
Thousands of commuters will have their travel time cut when the new underground stations are opened at Crows Nest, Victoria Cross, Barangaroo, Martin Place, Gadigal and Waterloo.
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New metro platforms have also been built at Central and Sydenham.
Transport Minister Jo Haylen on Tuesday afternoon confirmed passengers would have to wait “a little longer” for the service to be delivered.
Haylen said the railway was “99 per cent ready” but would not confirm a new timeline for opening.
Bus services designed to connect with the new metro line will start from Sunday as planned.
The minister said more than 11,000 hours of testing had been completed between Chatswood and Sydney, but more time was needed for the safety regulator to give its final approval.
“I’m not in the business of putting extra pressure on that independent regulator,” she said.
Haylen said another four exercises needed to be undertaken by Fire and Rescue NSW.
“Our processes needed a little more time,” she said.
“This is about independent assurance, not a risk to safety.”
Once the service is open, passengers will be able to travel from Victoria Cross in North Sydney to Barangaroo in three minutes, four minutes between Martin Place and Central, and get from Sydenham to Chatswood in 22 minutes.
During peak periods, driverless trains will run every four minutes in both directions, and initially every seven minutes in the inter-peak.
This will eventually increase to every five minutes during inter-peak times on weekdays and every 10 during off-peak and weekends.
Haylen apologised to commuters, admitting the delay was “disappointing”.
“I’ll be back here with more information for the travelling public so that you can plan your journeys,” she said.
The next stage of the project will extend services from Sydenham to Bankstown, meaning the T3 Bankstown Line will shut later this year for up to 12 months to complete the works.
Haylen admitted the closure would be a “painful and difficult process for those communities” but said the line would not but closed until there was a “high level of reliability” on the city section.