The university has abandoned plans to recruit medical students to begin studying there in 2020.
In a statement, Ulster University (UU) blamed the absence of a ministerial decision on funding the school for the delay.
The university said it was now working towards a target of recruiting students for September 2021.
It had initially been planned to open the graduate medical school in 2019.
However the project has been beset by problems and delays.
According to a previous review by the Department of Health, the North of Ireland needs at least 100 more medical students a year to meet the increasing demand for doctors.
However the department has also said expanding student numbers to that extent would cost £30m a year and see other services cut.
In September 2019, the head of the civil service, David Sterling, also cast doubt on the school’s future in a letter to Derry and Strabane District Council.
He said UU could not pay to run the medical school itself.
“Significant ongoing funding will be required from government if this is to proceed,” he wrote.
Ulster University has now said a business case for the medical school had been taken “as far as possible, in readiness for the political decision on funding”.
“The Department of Health has consistently confirmed the business case requires ministerial decision making to progress further,” it added.
“With the continued absence of the political infrastructure to enable the required funding decision, the opportunity to recruit a 2020 intake to the graduate entry medical degree programme has now passed.”
UU vice-chancellor Prof Paddy Nixon said the university had taken all possible steps within its control to open the medical school.
“The continued absence of political decision making for NI is a source of significant frustration and is time lost in educating the doctors we urgently need in our hospitals,” he said.
“This adjustment to our operational plans for the first cohort of medical students in 2020 is very disappointing for the healthcare sector locally and for prospective medical students keen to embark upon a rewarding and vital career path with us.”
UU previously said it had submitted a business case to the department on 21 October but it remains at an outline stage.
“We cannot spend money we do not have.”