The nationalist Social Democratic and Labour Party have said they will oppose adjournment of the Northern Ireland Assembly.
The political institutions moved a step closer to collapse or suspension after the party said it would not support the Democratic Unionist ultimatum.
First Minister Peter Robinson has said his ministers will resign - forcing the fall of Stormont power sharing - if a crunch meeting of the parties this afternoon does not agree to adjournment or the British Government does not suspend them.
SDLP leader Dr Alasdair McDonnell said: "Unlike others in the political system who have rushed to judgement we have been steady and spoken to everyone interested in the current crisis, including the Irish Government this morning.
"Our decision is to oppose the adjournment because it is not a solution."