Another Stormont election should be called after Friday, Sinn Fein urged.
The party said there was little prospect of agreement on the way forward amid faltering talks with the DUP and British Government on restoring the power-sharing institutions.
Good Friday is the deadline for a deal and Northern Ireland Secretary James Brokenshire said he would make a call on the state of negotiations over the Easter weekend to enable him to move Westminster legislation once MPs return from recess on April 18.
Sinn Fein's leader at Stormont Michelle O'Neill said: "We remain committed to trying to deal with the issues which are there.
"We have set out what we need to see delivery on and we need to see a different approach from the DUP and, indeed, from the British Government.
"But post-Friday I think it is over to the electorate to have their say about the future.
"But clearly Sinn Fein want to make these institutions work, but they have to work for all our citizens."
After Friday Mr Brokenshire will have to consider legislating to pass a budget for public spending in Northern Ireland and could introduce direct rule by ministers from Great Britain.
Mrs O'Neill replaced Martin McGuinness as the party's most senior politician in Northern Ireland.
She reiterated Sinn Fein's demand that DUP leader Arlene Foster could not be a Stormont minister until the public inquiry into the renewable heat incentive (RHI) had been delivered.
Mrs Foster was the minister who oversaw the introduction of the botched green energy scheme predicted to cost the taxpayer around £490 million.
Mrs O'Neill briefed media at Stormont.
She said: "We are at a critical period and without delivery and addressing those fundamental issues there is very little prospect of achieving a political agreement here on the way forward."
Two of the main stumbling blocks are the contentious issues of Irish language protections and how to deal with the toxic legacy of Troubles killings.
The Democratic Unionists have accused the republican party of peddling "doom and gloom" and questioned whether it was actually committed to the restoration of devolution.
The two main parties are taking part in discussions along with Stormont's other three main parties, the Ulster Unionists, SDLP and Alliance Party, and the UK and Irish governments.
Devolution crashed in January over a row about the DUP's handling of the RHI.
SDLP leader Colum Eastwood accused the DUP of failing to grasp that there "needs to be respect for each other's identity".
He said: "I often hear people asking me if Sinn Fein are committed. Well that's a question for Sinn Fein. But if the DUP want that question answered they should call their bluff. They should support all of the things they agreed to in the past - sign up to an Irish Language Act, accommodate another identity - then we will see who is really committed.
"At times, in many of the meetings, the DUP haven't quite grasped the fact that things have changed. They haven't quite grasped that if we just allow the Assembly, the majority of the members in there, to decide a lot of those issues then we could get things moving forward."
Mr Eastwood said he got the sense during the negotiations that "some people are going through the motions".
"That is very, very frustrating. We don't think any of this is insurmountable. I'm not convinced everybody is in the same place.
"We have a couple of days left to get this done. Let's try and do it."