HMS Caroline, the only surviving ship from the First World War Battle of Jutland and one of Belfast's top visitor attractions, will remain closed until next year due to funding pressures.
The National Museum of the Royal Navy (NMRN) said the decision was taken after an operations and funding agreement could not be reached with the Department for the Economy.
NMRN operates HMS Caroline in the Titanic Quarter on behalf of the Executive.
It has been temporarily closed since March 17 in line with public health advice.
The operational agreement for HMS Caroline expired on June 30, leaving NMRN unable to run the exhibit.
It says it has been under "extraordinary financial pressure", with a funding gap in excess of £6m, and has warned that jobs could be lost if the situation is not rectified.
While the ship is owned by NMRN, it has been open to visitors through the agreement with Stormont.
NMRN said it has "worked extensively" with DfE to establish a new operational agreement and to recoup the significant sums in running costs since the ship opened to the public in 2016, which it claims are still owed to it.
Director general Dominic Tweddle said: "This is a desperate situation for the museum and especially for our incredibly dedicated team at HMS Caroline.
"We are fortunate that we have a few weeks of being able to support staff's salaries under the Coronavirus Job Retention Scheme whilst we continue to fight to secure the future of the ship and its team.
"However, if we are not able to sway DfE from its current position then HMS Caroline will not reopen until 2021 and those jobs will have to be made redundant".
The department said visitor numbers are key to the sustainability of the attraction, but these have been "disappointing to date, resulting in operational deficits".
It said it had been "concerned about these deficits for some time" and worked closely with NMRN to make the attraction more profitable, reduce deficits and ensure greater value for the use of public funds.
It added: "The department has deployed external consultants to fully establish and confirm the totality of this deficit and this work is still ongoing.
"It is expected to report in August 2020. However, to help with cash flow issues during the Covid-19 crisis, the department has already made a substantial interim payment to NMRN."
"The agreement that the department had with NMRN to operate the attraction expired on 30th June.
"The NMRN took the decision not to renew this agreement without a revised funding model being put in place and they notified the department of this on 10th June.
"This did not leave sufficient time for the department to formulate a new funding model, redraft a new operating agreement or to procure a new operator of the attraction."
The department said it had agreed with NMRN to extend the closure of HMS Caroline until December 31 and will fully examine all options and costs for its future.
Belfast has been home to HMS Caroline, a finalist of the 2019 Art Fund Museum of the Year, since 1924.