Sir Jeffrey Donaldson has signalled that his party may seek to veto extra cash from Stormont and the British government for the redevelopment of Casement Park.
Within 24 hours of Uefa giving the green light to the Republic and UK's joint bid to host Euro 28, the DUP leader said there would be a "lot of questions" if money was found for the west Belfast stadium while the north faces a budget crisis.
Sir Jeffrey said he did not know if the GAA stadium would be built in time for the tournament, insisting that he would not support extra funding for the project from Stormont.
His intervention may be an impediment to work beginning on the 34,000 capacity stadium, after years of funding wrangles and delays.
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The GAA has said it is confident that funding will be in place to begin work next spring.
The project has been hit by soaring costs, with an original price tag of £77.5 million now believed to have spiralled to well above £100 million.
Casement Park Project Sponsor Stephen McGeehan discusses the redevelopment
The GAA is part-funding the project but agreement has yet to be reached on the size of its contribution. Taoiseach Leo Varadkar said last week that the Irish government would be prepared to foot some of the bill.
The DUP leader told the PA news agency that his party would not break the principle of equitable funding for sports stadiums across the region.
"We have been very clear, the funding that was set aside for regional stadia in Northern Ireland, that was Windsor Park for football, Ravenhill for Ulster Rugby and Casement for GAA, that was done on an equitable basis, we will not be withdrawing from that principle, we will not see that principle undermined," he said.
"We are very clear, the (Stormont) executive doesn't have money, the additional money that is required for this stadium."
The Lagan Valley MP speculated that the eventual cost of the stadium could reach between £150m-£200m, saying "construction costs are going up all the time".
He said the British government was pledging to meet some of the additional costs for Casement while there were questions over funding for public services.
Sir Jeffrey said he would have concerns about cash from Dublin for the project "in the circumstances where the principle of equality is not respected".
Sinn Féin vice president Michelle O'Neill has previously described the hosting of Euro 2028 games in Belfast as the "opportunity of a lifetime".
SDLP Colum Eastwood told The Irish News that the redevelopment of Casement Park was an "executive priority project".
"The British and Irish governments have committed to allocating additional funding to get it across the line in time for the Euro 2028 – it is going to happen whether Jeffrey Donaldson likes it or not."
