The Treasury cannot expect Northern Ireland to absorb the cost of tackling swine flu on its own, the First Minister has said.
Peter Robinson warned it would cost £77 million to deal with the pandemic including treatment and vaccines.
The Executive is due to discuss the problem tomorrow.
Mr Robinson said: “The Treasury feels that this is something that can be absorbed within the devolved administrations. I don't believe this is sustainable.
“They could argue that there are certain elements of the cost that can be absorbed and dealt with but there's no good reason to believe that the vaccine, which could not have been predicted or costed beforehand, would be a cost to the local administrations.”
He has agreed with the Welsh and Scottish administrations to lobby Treasury on the matter.
“£77m will make quite a hole in the budget no matter what way we decide to handle the cost,” he predicted.
Mr Robinson told the Assembly the Treasury should fund the cost of the swine flu vaccine, mindful of the fact that spending cuts of £370m are needed here next year.
“That would take some of the sting out of the cost element but it still leaves us with a hefty bill and the Executive will still have to decide, and I think starts the decision making on Thursday, with the costs that are coming our way,” he added.
Meanwhile, a child at Co Antrim preparatory school Dalriada contracted the virus recently and parents were asked to keep children at home if they displayed symptoms.
The Department of Health's assumptions are that up to 30% of the population may become ill with flu at some point during the pandemic; up to 1% of people who become ill with flu may require hospitalisation and up to 0.1% of people who become ill may die from the virus.