There is a danger that devolution could collapse
Northern Ireland's political process has entered yet another critical phase as the DUP and Sinn Fein struggle to reach agreement on the transfer of policing and justice powers from Westminster to Stormont.
BBC News Online examines the latest issue which is threatening to cause the breakdown of devolution.
Why weren't policing and justice powers moved to NI when other functions were devolved under the
Good Friday Agreement?
Policing and criminal justice were highly contentious matters and a definitive way forward could not be reached at the time.
Many nationalists felt they had not been well-served by the police and wanted radical reform.
Unionists were uneasy at the prospect that those who had attacked the police could be involved in overseeing them.
The Good Friday Agreement, signed in 1998, said the powers would be devolved at some point in the future with the approval of the political parties.
The parties also agreed to the setting up of independent commissions which led to major reforms of the police and criminal justice system.
Why is the devolution of policing and justice powers such a contentious issue?
Sinn Fein has always said it understood that policing and justice powers would be devolved once it dropped its longstanding opposition to the police.
The party did so after the
St Andrews Agreement.
However, it says the DUP has so far reneged on its part of the deal, which would have seen policing and justice powers devolved.
The DUP has said that, while it wants to see the powers devolved, it will not move on the issue until there is "unionist community confidence" in doing so.
So, while Sinn Fein wants the powers devolved to ensure it keeps republicans behind the political process in the face of growing dissident activity, the DUP is concerned it could lose ground to unionist hardliners if it is seen to be conceding to Sinn Fein demands.
The DUP also wants the abolition of the
, a body set up to rule on whether or not contentious parades in Northern Ireland should take place, in return for setting a date for the devolution of policing and justice powers.
This is unacceptable to Sinn Fein.
What has brought the issue of policing and justice to the fore?
Sinn Fein has recently escalated its efforts to get the powers transferred to Stormont.
Dissident republican activity has increased in recent months
Before Christmas, the party's deputy leader, Martin McGuinness warned that Northern Ireland's political institutions were unsustainable if the impasse continued.
The British and Irish governments have also said they want the issue resolved as soon as possible and have offered a
"generous financial settlement"
of up to £1bn for a devolved justice department if a deal can be reached in the coming months.
With a general election looming in May, the DUP is aware that the issue is a potential vote loser for them and have been cautious in their approach.
However, Sinn Fein threats to withdraw Martin McGuinness as deputy first minister, coupled with DUP fears of a voter backlash following the Iris Robinson scandal, have meant the DUP has had to go to the negotiating table.
If Sinn Fein were to decide that Mr McGuinness should resign, the joint nature of the roles of first and deputy first ministers would mean that DUP leader Peter Robinson would also be forced out of office, bringing about the collapse of the executive and raising the possibility of an assembly election.
Why is the relationship between Northern Ireland's two main parties so poor?
The Northern Ireland Executive
is a mandatory coalition between unionists and nationalists.
The two main coalition parties, the DUP and Sinn Fein, have always been on the opposite poles of Northern Ireland politics.
During the Troubles, the IRA, which was seen as the paramilitary wing of Sinn Fein, attempted to kill DUP members.
In the past, it was the DUP accusing the more moderate Ulster Unionist Party of cosying up to Sinn Fein.
However, since the restoration of the Northern Ireland Assembly after the St Andrews Agreement in 2006, the DUP has found itself in the position of having to govern Northern Ireland hand in hand with a party it had previously refused even to talk to.
For many DUP voters and members, this relationship was too much to take and led to the party's former MEP, Jim Allister, setting up the TUV party in the wake of the St Andrew's Agreement.
Relationships between the DUP and Sinn Fein are, however, far from being as cordial as the TUV would like people to believe.
Recently, Sinn Fein President Gerry Adams wrote on
about the numerous times senior DUP members had refused to share a lift with him at Stormont.
Peter Robinson and Martin McGuinness have been involved in negotiaions
As BBC Ireland correspondent Mark Simpson observed: "If republicans and unionists really cannot go down three floors in a lift together, can they run Northern Ireland together?"
The DUP says Gerry Adams is exaggerating the personal problems, and that the real differences are on policy, with Sinn Fein simply being constantly intransigent.
They are accused of having an "our way, or no way" attitude.
What happens if the issue is not resolved?
If a deal cannot be reached on the devolution of policing and justice and Sinn Fein consequently withdraws Martin McGuinness as deputy first minister, the executive will collapse.
The rules state that if either the first or the deputy first minister resigns, the other must also leave their post.
The parties at Stormont will then have a period of seven days to elect a new first and deputy first minister.
If the politicians failed to reach agreement, this would trigger an assembly election - the date would be set within a "reasonable period" by Northern Ireland Secretary Shaun Woodward.
There is a possibility that a judicial review could force him to call an immediate election.