Queen's University in Belfast has warned staff it may have to make compulsory redundancies in an effort to save money, the BBC has learned.
The university announced in April it was cutting 236 posts in 2015/16 through a voluntary redundancy scheme.
But in an email to staff, Queen's said: "The required pay savings... have not been fully achieved."
As a result, staff who have not already applied for voluntary redundancy have now been invited to apply.
They will have until early October to come forward.
But the email also says: "In the event that the required savings have not been made within schools/directorates, formal processes will regretfully require to be implemented."
University sources have confirmed those "processes" may include compulsory redundancies.
The university was unable to clarify exactly how much it had missed its pay savings targets by and how many staff had been offered voluntary redundancy.
Queen's funding from the Department for Employment and Learning was cut by £8m earlier this year.
In a statement to the BBC, a Queen's University spokesperson confirmed that the pay savings to be delivered through the voluntary redundancy scheme had not been achieved.
They also said a strategic review is ongoing "to determine the future size and shape of the institution" and that recommendations would be presented to the university senate during this academic year.
The BBC understands that review is likely to recommend some subject and course closures.
Alun Harpur, president of the Queen's branch of the University and Colleges Union (UCU), which represents staff said the mood among staff was "one of uncertainty and anxiety".
"They don't know who will be targeted for compulsory redundancy if the university is intending to go down that route," he said.
"The union has not yet been provided with the necessary information in terms of staff numbers involved or indeed the amount of savings that the university is short by."
He also called on the university to provide clarity on the status of the voluntary redundancy scheme that is still open to staff.
"We don't know how many people have applied for it, we don't know how many people were rejected, how many people were accepted and we don't know what areas they were from, so we've got a lot of information that is needed on that before we even start thinking about compulsory redundancies," he said.
"Equally, the university is supposed to, under its own policy, look at all alternatives before it moves to compulsory redundancies."
In a separate development, the UCU have written to management at Ulster University questioning the legality of the redundancy process there.
Following receipt of a business case from the university, they have accused management of "intimidating" staff into applying for voluntary redundancy, and not carrying out adequate consultation.
The UCU letter claims that "the employer's behaviour potentially constitutes an unlawful failure to consult," and they have called for the scheme to be postponed.