Senior unionists will meet today to discuss the next phase of their protest against a decision to ban a controversial Orange Order parade from passing a nationalist neighbourhood.
The Democratic Unionists and Ulster Unionists walked out of a political talks initiative at Stormont yesterday to highlight their anger at the Parades Commission move and ministers from both parties have pulled out of planned cross border meetings in Dublin today with counterparts in the Irish government.
The steps were part of a pledged "graduated response" to the commission's determination. The next moves are set to be formulated when representatives from the two parties and a range of smaller unionist and loyalist parties meet to discuss the crisis.
The developments have placed a question mark on the future viability of the power sharing administration, with DUP First Minister Peter Robinson having gone as far as to state that the institutions are "under threat".
In issuing its determination yesterday, the Government-appointed commission cited the potential for public disorder and negative impact on community relations among its reasons for preventing the contentious July 12 evening parade proceeding along north Belfast's Crumlin Road, which is adjacent to the nationalist Ardoyne neighbourhood.
While both loyalists and republicans have engaged in serious rioting linked to the parade in recent years, the DUP and UUP insisted the commission had given in to the threat of republican violence.
The two main unionist parties issued a joint statement endorsed by representatives from smaller unionist and loyalist parties in the region, including two with links to paramilitary groups. All the signatories said they were also cutting ties with the Parades Commission.
As the Orange Order denounced the decision to restrict the parade as "preposterous", Mr Robinson has said the commission's stance had put the powersharing institutions in danger.
"The institutions have been put under threat by the behaviour of the Parades Commission and those who threaten the Parades Commission," he said last night.
"It is up to us to seek a peaceful response."
Earlier Sinn Fein Deputy First Minister Martin McGuinness said unionists needed to explain exactly what "graduated response" meant.
"I hope it doesn't mean a threat to the institutions," he said.
"I have made it clear that these institutions have provided very important stability."
In recent years when the Orange Order parade was given permission to pass the Ardoyne, republicans rioted.
When it was banned last year, loyalists rioted in the nearby unionist community in Woodvale.
Loyalists have manned a protest camp at the volatile community interface ever since, requiring a policing operation costing around £10 million.
The political talks at Parliament Buildings in Belfast between the five parties in the executive collapsed on only their second day.
They were established by Mr Robinson and Mr McGuinness in an effort to break the impasse on disputes over parades, flags and the past. One of the issues being debated was a potential replacement for the controversial Parades Commission.
Unionists were clearly preparing themselves for the course of action yesterday, as the lengthy statement outlining their intentions was circulated minutes after the commission ruling was issued.
Former US Secretary of State Hillary Clinton expressed hope the issues could be resolved.
"I care deeply about what happens in Northern Ireland as does my husband," she said.
"I know there are still obstacles in the way of trying to achieve all the goals that everyone hopes for."
In an interview with RTE Radio 1, she added: "I pray that everyone keeps their eyes on the ultimate goal that people can live in peace, security and reconciliation."
Sinn Fein president Gerry Adams said the Irish and British governments should not acquiesce to unionist threats.
"The walk out by the unionist parties and their threat to pull down the political institutions is part of an escalating crisis within the political process in the north which has been going on for some time," he said.
"The pretext for yesterday's walkout, and a statement which was prepared in advance, is the Parades Commission's ruling that an Orange feeder parade be allowed to pass Ardoyne on the morning of the 12th but not in the evening.
"Sinn Fein has been actively trying to focus the Irish and British governments on problems within the process for some time."
Mr Adams also said he had warned Prime Minister David Cameron that the political process in the north is deteriorating.
"We told him that the British and Irish governments, as co-equal guarantors of the agreement, should not acquiesce to unionist threats and must ensure continuing progress and this has to include implementing agreements already made that are the sole responsibility of the two governments," he said.
"Unionist leaders cannot divorce themselves from the likely consequences of their call for protests against the Ardoyne decision by the Parades Commission."