London's Crossrail project has been hit with fresh delays and might need an extra £450m, its board has said.
The route - known as the Elizabeth Line - was initially due to open in December 2018 but has faced numerous delays.
Crossrail has now said the line's central section, from Paddington to Abbey Wood, would be ready to open "in the first half of 2022".
The Mayor of London is said to be "deeply disappointed" with the latest delay.
Transport for London's new commissioner, Andy Byford, has been asked by City Hall to review Crossrail's latest update including any extra money the project may need.
Mr Byford also said the delay was "disappointing" and said the Department for Transport (DfT) would also look at Crossrail's plans.
The government has also launched a new "acceleration unit" designed to speed up road and rail infrastructure upgrades.
Transport Secretary Grant Shapps revealed that a team of specialists will join the DfT to tackle delays to infrastructure projects caused by the pandemic.
Crossrail's new date comes after the team behind the project said last month that the route would not meet its then-summer 2021 target opening.
Currently the trains run between Liverpool Street and Shenfield, Essex as well as between Paddington and Reading, Berkshire. There is also a line from Paddington to Heathrow operating.
But the ongoing Covid-19 pandemic is one of the reasons behind the new delay to completing the central section of the line, which will run mostly through tunnels.
The team said social distancing meant that a maximum of 2,000 people were now allowed on Crossrail sites - less than 50% of the staffing levels before the pandemic.
The project's boss said their "focus remains on opening the Elizabeth Line as soon as possible" and that they have a "comprehensive plan".
Crossrail's CEO Mark Wild said the project is in its "complex final stages".
"It is being completed at a time of great uncertainty due to the risks and potential impacts of further Covid outbreaks," he added.
"We are working tirelessly to complete the remaining infrastructure works so that we can fully test the railway and successfully transition the project as an operational railway to Transport for London."
By BBC London's Transport correspondent Tom Edwards
The crucial point to remember with these "opening dates" is no one actually knows when Crossrail will start operating.
These dates are now an educated estimate but so many dates have come and gone that no one will trust the latest one.
Crossrail already had problems and due to Covid-19, inevitably construction slowed down and the complex testing of the hi-tech signalling systems will now only start in October.
Train testing then starts but more problems will probably crop up. There could also be more delays due to more Covid outbreaks.
Don't forget this further delay has a big knock-on on TfL's finances which are already in a dire state.
It will also affect all those businesses and tenants up and down the line who have been paying increased rent on the promise of Crossrail.
Until it opens - Crossrail is shut.