Crucial talks to save Northern Ireland's powersharing political institutions are due to begin in Belfast today.
The negotiations, facilitated by the British and Irish governments, will involve representatives from the five main parties which make up the mandatory coalition Executive at Stormont.
Topping the agenda at Stormont House will be issues around paramilitary activity, the budget and the implementation of controversial welfare cuts.
Northern Ireland Secretary Theresa Villiers warned politicians not to waste the opportunity to build a better future.
She said: "I recognise the scale of the task ahead. We are dealing with very difficult issues.
"But Northern Ireland's political leaders have achieved great things over the past 20 years working together. That same spirit needs to be brought into these talks.
"We must not let this opportunity to build a brighter, more secure future for Northern Ireland slip away."
The devolved Assembly, which was restored in 2007, has been teetering on the verge of collapse following the murder of a man by Provisional IRA members last month.
Kevin McGuigan, 53, was shot dead in a suspected revenge attack for the murder of his one-time associate and IRA commander Gerard "Jock" Davison, 47, three months earlier.
A police assessment that individual members of the PIRA were involved alongside dissident republicans and criminal elements has rocked the political establishment and prompted unionists to remove all but one ministers from the Executive.
As the crisis deepened First Minister Peter Robinson, whose Democratic Unionist Party (DUP) had sought an adjournment or suspension of Stormont also temporarily stood aside, saying it could not be business as usual.
Unionists had said the issue of paramilitary activity was crucial to their participation in any talks process.
On Friday, the Government announced an independent assessment of paramilitary criminality and pledged increased funding to tackle cross border organised crime such as fuel laundering and smuggling.
Mr Robinson's attendance had been uncertain after he was rushed to hospital having suffered an adverse reaction to prescribed medication.
However, the 66-year-old, who had a heart attack in May, was discharged on Sunday evening and a DUP spokesman confirmed he would be at Stormont.