Ulster Unionist leader Jon Burrows said he did not want to sound “defeatist” and would continue to engage with the government.
But he said there was a real prospect that it would be resolved in time to avert the potential of strike action by health care workers waiting on pay uplifts for this year.
Speaking before talks with the secretary of state, Alliance’s Agriculture Minister Andrew Muir said it is now “make your mind up time” for the executive.
“This needs to be resolved not in weeks or months, but days. We need to come to a final conclusion and give certainty to people who deserve proper pay but also in terms of investment in public services we need to get this done,” he added.
Speaking on BBC NI’s The View programme, Social Democratic and Labour Party (SDLP) leader Claire Hanna said a budget is “an agreement to take responsibility and an agreement to prioritise”.
Her party, which is the official opposition in the legislative assembly, is “very clear about the severe constraints,” she said, but added: “the fact is by not having a budget in month eight of this financial year, everybody who’s trying to operate in that budget is running at 95%”.