FILE PHOTO: People walk through the Crossrail Place Bridge in the Canary Wharf financial district of London, Britain, December 7, 2018. REUTERS/Simon Dawson/File Photo

LONDON (Reuters) - London’s beleaguered multi billion-pound Crossrail project, already years behind schedule, will be further delayed until late 2021, the British capital’s transport operator said on Monday.

The train line, billed as Europe’s most ambitious infrastructure project, has been repeatedly delayed by problems with safety testing and signalling systems and Transport for London (TfL) said last year its cost could rise to $23 billion (17 billion pounds).

TfL Commissioner Mike Brown told the London Assembly Budget and Performance Committee on Monday that the section of the new link between the rail hub of Paddington and Abbey Wood in southeast London was now expected to open between September and December 2021.

Brown said TfL had struck a confidential commercial deal with the Canary Wharf Group to remove the risk of TfL paying damages if the link between the Canary Wharf financial district and Heathrow airport was not completed by December that year.

“We’ve looked at a delay until the later stages of 2021, in terms of our business planning assumption,” Brown said, adding that the project was in “disarray”.

“The assumption we’ve made is I suppose at the pessimistic end but it’s the pragmatic end,” he said.

Brown said a critical issue was making sure the Siemens system SIEGn.DE on the tracks was compatible with the system built by Bombardier BBDb.TO in the trains.

In November, TfL said the project could cost an extra 650 million pounds and not open until 2021, putting it more than two years behind schedule. It was originally due to be opened by Queen Elizabeth in December 2018..

Rebranded as the Elizabeth Line in 2016, it is expected to carry about 200 million passengers a year and alleviate pressure on London’s 19th century underground network, known as the Tube.