The Ulster Unionists have denied that their decision to vote no in a crucial assembly vote on the devolution of policing and justice will plunge the power-sharing institutions into crisis.
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"There isn't a crisis in Northern Ireland", UUP Strangford MLA David McNarry told UTV Live Tonight.
"The Assembly is not going to crash (...). Peter Robinson and his DUP colleagues along with Martin McGuinness and Sinn Fein will walk hand-in-hand into the lobby to vote yes to this".
"We are taking a principled stand."
Under the Hillsborough agreement, policing and justice powers will be devolved on 12 April, if a resolution jointly tabled by the First and Deputy First Ministers gets cross-community support in an Assembly vote on Tuesday.
Sinn Fein and the DUP have enough MLAs in the Assembly to secure the required cross-community vote.
'Bullied'
On Monday night, UUP leader Sir Reg Empey said his party's executive endorsed a decision to vote against the proposals, claiming the power-sharing government is not ready to take on the new powers.
"We are not prepared to be blackmailed. We are not prepared to be bullied. We've been around a long time. Our strength is our history", Sir Reg said.
"We are prepared to go forward and look to the future," he added, "but not under the cosh of all this blackmail and bullying."
A statement issued by the Ulster Unionist party added:
"The Ulster Unionist Party wants to see these powers exercised by a local minister accountable to local representatives. However the conditions must be right - we must show that the Assembly can handle the power that it has before it takes on even more contentious powers."
Secretary of State Shaun Woodward said a UUP rejection would fail to block the measures, but would send a divisive signal on the first anniversary of the murder of police officer Constable Stephen Carroll, who was shot by the Continuity IRA as he answered a call for help in Craigavon, Co Armagh, on 9 March 2009.
Following the remarks, the UUP condemned "the inappropriate behaviour of the Secretary of State for Northern Ireland".
Their decision was announced amid reports of a late intervention by former US President George Bush, urging the UUP's allies in the Conservative Party to use their influence with Sir Reg.
The Guardian newspaper claimed that Mr Bush asked Conservative leader David Cameron to persuade the Ulster Unionists to back the deal on Tuesday.
Shadow Northern Ireland secretary Owen Paterson confirmed that Mr Bush had had "a very constructive and friendly conversation" with Mr Cameron.
US Secretary of State Hillary Clinton also phoned the UUP leadership urging their support.
'Colossal'
"I think they made a colossal mistake," former DUP leader Ian Paisley told reporters gathered in Ballymena as he announced his retirement as MP for north Antrim.
"But I think that their colossal mistake was to join up with the Conservatives, because unionism is not conservatism. Unionism is a rallying of all the people who want to keep the Union and keep the place British", Mr Paisley said.
Alliance leader David Ford, who is tipped to become Justice Minister, said that if the Ulster Unionists failed to back the Hillsborough deal on Tuesday, the Conservative Party should end its link with the party.
Mr Ford said: "If the UUP vote no on the agreement then the Tories face no option but to end the link with them to save what credibility they have left on Northern Ireland.
"If the Tories allow this sham marriage to continue after a no vote, they will demonstrate a total lack of principle and leadership."
The comments came after a dramatic day at Stormont where two separate government opinion polls were unveiled to show major public support for the devolution of the policing powers.
The UUP was the only party to boycott the unveiling of the Hillsborough Agreement last month.
Sir Reg repeatedly complained that he had been kept in the dark during the marathon talks between the DUP and Sinn Fein.
Last month, he told UTV his party would not sign up to the deal unless a "consensus" was found to solve the education debate.
He has also been highly critical of what he calls the "dysfunctional nature of the executive".
Sinn Fein junior minister Gerry Kelly said the UUP was playing "crude politics" with people's future.
"I think the overwhelming majority of people want this to happen.
"I think it's going to happen tomorrow and we are delighted to be at this point," he said.
DUP leader Peter Robinson repeated that he believed the Hillsborough agreement represented a good deal for unionism.
"We have an agreement that is sound. It provides safety and security to the people of Northern Ireland", Mr Robinson told UTV.
© UTV News