LEGAL action over a construction contract could delay the opening of a new university campus by another two years.
The Ulster University (UU) venture - the largest of its kind in the north - may now not be ready until at least 2022.
Building work is continuing to transform the 'art college' campus on York Street, at the top of Royal Avenue in Belfast.
This will see most courses transfer from Jordanstown and student numbers in the city rise from 2,000 to 15,000.
Late 2018 was an agreed "key milestone" - the date on which work was expected to be complete. However, the university later took the decision to move students at the start of the 2019 academic year. No explanation for this delay was provided.
This was pushed back further again with UU saying it would welcome staff and students for the first full teaching year in autumn 2020.
The university dismissed previous claims of a five year delay as "absolute nonsense".
In addition, the total estimated cost has increased from £250 million to £263m.
The first phase of construction at UU is already complete and open.
A joint venture between Lagan Construction Group and Portuguese firm Somague Group, was awarded a £150m contract - part of the initial overall £250m - for phase two.
It has been confirmed that legal proceedings have been commenced by the university to resolve some aspects of the contract. It is understood this involve claims the works were "not carried out in accordance with the contract".
It has now been reported that Lagan and Somague have written to the university to warn that work will likely now take until 2022.
A UU spokeswoman said proceedings were commenced by the university to "resolve some aspects of the contract".
While not commenting on the 2022 date, she added that on any large and complex capital project, "adjustments to timeframes are to be expected".
"Whilst any delay is disappointing, it is not uncommon given the scale of our development," she said.
"We are working closely and in partnership with our lead contractor to move beyond these challenges in the continued construction of a world class facility in the city, of which the university and our lead contractor can be proud.
"The move into the new building in 2020 is based upon the latest contractors programme. As any update to the timeframes are agreed, we will make that information available."
A spokeswoman for Lagan Construction and Somague's joint venture said: "The Lagan Somague joint venture continue to work collaboratively with Ulster University towards completion of this iconic project in Belfast."
