Plans for a new tram-train link between Sheffield and Rotherham have been hit by another delay.
The £58m project will enable trams to run on tramlines in the city centre and onto train tracks between Meadowhall and Rotherham.
It was originally due to begin operating in 2015, but was delayed until 2017.
But Network Rail has now announced that the 2017 date will be missed.
A spokesman for South Yorkshire Passenger Transport Executive said: “We have been notified that Network Rail can no longer complete the tram train infrastructure works to timetable, for passenger services to start in early 2017 as planned.
“We acknowledge that the design, planning and construction to allow the vehicles to run on the heavy rail network is complex.
However, we are extremely disappointed in this news.
“All parties remain committed to the delivery of the project and to starting Tram Train services at the earliest possible time.”
A new date is expected to be announced in the summer.
Stagecoach Supertram unveiled the first vehicle at the depot in November.
Paul Blomfield, MP for Sheffield Central, has condemned the latest delay to the Sheffield to Rotherham tram-train scheme.
He said: “The Sheffield to Rotherham tram-train scheme is becoming the never never project. It was agreed seven years ago by the Labour Government. It took three years to secure funding from the Tory-led Coalition and since then we’ve seen planned start dates in 2015, 2016 and 2017 come and go. Now we don’t even have a launch date.
“This Government talks about a Northern Powerhouse, but its proposed closure of the Sheffield BIS Office, together with the delay to this flagship transport project, makes it look like empty words. They talk the talk. They should walk the walk.”
Mr Blomfield has written to the Secretary of State for Transport and the Chief Executive of Network Rail to seek assurances on the project.