Northern Ireland's political leaders have been given two weeks to save powersharing after the UK government announced a final bid to salvage the crisis-hit institutions.
The region's secretary of state Karen Bradley and Irish foreign affairs minister Simon Coveney have confirmed that a fresh round of cross-party negotiations will begin next Wednesday.
Mrs Bradley said there were still "significant difficulties to overcome" but she believed a resolution is possible.
The region has been without a properly functioning powersharing executive for more than a year.
The Democratic Unionist/Sinn Fein-led coalition imploded in a row over a botched green energy scheme but the rift between the two largest parties subsequently widened to take in more long-standing cultural and legacy disputes.
Proposals to protect Irish language speakers, the ban on same-sex marriage and a lack of consensus on how to deal with the legacy of the Troubles remain key areas of disagreement.
Sinn Fein's participation in any new talks had been in doubt, with the party insisting it would not take part if there was not a new dynamic.
The party's Stormont leader Michelle O'Neill confirmed Sinn Fein would engage after holding a meeting with Mrs Bradley at Stormont on Thursday morning.
Mrs O'Neill said the anticipated timeframe for the negotiations was two weeks.
"We are determined to find a resolution that sees the institutions restored and delivering rights for all citizens," she said.
"Credible, sustainable institutions can only be based on equality, respect and genuine partnership government.
"These talks will be a test of whether the British government and the DUP are finally willing to endorse these basic principles."
She added: "I told Karen Bradley that the British government is not a neutral and impartial player and there must be a change of approach on her part."
With the region having no local ministers to agree a budget for the next financial year, the UK Government will face increased pressure to reintroduce a form of Westminster direct rule if the latest talks bid fails.
Mrs Bradley characterised the talks as the "last opportunity" to find a resolution.
She said failure to make "rapid progress" would mean her government would face significant decisions, including setting a budget for the new financial year.
MLA pay and a fresh election would also be looked at and "ultimately other arrangements" she warned.
Mrs Bradley said the need for a solution was "urgent" and the political consequences of failing to reach a deal would present a "significant setback to the progress" made since the Good Friday Agreement of 1998.
Mr Coveney said all parties were "very conscious of the time pressures".
"I think we are talking about weeks rather than months here," said the Irish deputy premier.
"The pressures have been building for some months now in the context of decisions that need political input from a devolved government here in Northern Ireland that can't be made in the absence of the being possible."
The Secretary of State was later forced to clarify remarks she made in a subsequent sit-down round of questions with the print media about the DUP's confidence and supply deal with her minority government at Westminster.
She had indicated to reporters the release of the full £1 billion earmarked for the region as part of that agreement was dependent on the restoration of powersharing.
"A budget that's going to be administered needs ministers to administer it," she said. "It needs Stormont to do it."
However, Mrs Bradley later contacted the Press Association to say her comments on the £1 billion had been "possibly clumsy".
She insisted the Government acknowledged the unique circumstances of Northern Ireland and while the preference was for devolved ministers to administer that money, it would not be held back in the event of Stormont not returning.
Mrs Bradley is just over a week into the job. She replaced James Brokenshire after he resigned from the Government on health grounds.