Crunch talks to save Northern Ireland's powersharing political institutions are due to start in Belfast today.
Representatives from the five main political parties will take part in the negotiations at Stormont House, which will focus on paramilitary activity, the budget and the implementation of welfare cuts.
The devolved Assembly has been teetering on the verge of collapse since 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.
The resulting turmoil led to Democratic Unionist Party leader and First Minister Peter Robinson temporarily stepping aside.
Mr Robinson will take part in the talks despite being admitted to hospital on Saturday.
Northern Ireland Secretary Theresa Villiers warned politicians not to waste the opportunity.
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."