**Ex-US president George W Bush has asked David Cameron to try to get the Ulster Unionists to back devolution of justice and policing in Northern Ireland.**The NI Assembly is due to vote on the transfer of the powers from Westminster, a day after the UUP confirmed it would reject it.
The Conservatives have an electoral pact with the UUP, prompting Mr Bush’s call to Tory leader Mr Cameron.
If the vote is passed, it will lead to the powers being devolved by 12 April.
The vote at Stormont is the first hurdle facing the Hillsborough Castle deal, which was struck last month thanks to an historic agreement between the Democratic Unionist Party and Sinn Fein.
In his phone call from Mr Bush on Friday, Mr Cameron made it clear that, despite his party’s links with the UUP, he was not in a position to tell them what to do.
The BBC’s Ireland correspondent Mark Simpson said of the discussion: “Once again, the Stormont Assembly is attracting international attention.”
On Monday, the UUP accused Northern Ireland Secretary Shaun Woodward of political and emotional blackmail after he urged the Ulster Unionists to vote in favour of devolution.
UUP deputy leader Danny Kennedy said Mr Woodward had “disgracefully” linked the vote to the anniversary of the murder of Constable Stephen Carroll.
The vote takes place exactly a year after the police officer was murdered by the Continuity IRA in Craigavon.
ANALYSIS
Mark Simpson, BBC Ireland correspondent****Devolving policing and justice
It took 10 days and nights to negotiate the Hillsborough Castle deal, and now it faces its first hurdle. Tuesday’s vote at Stormont is important - just ask former President George Bush and the current US Secretary of State Hillary Clinton.
They have been involved in trans-Atlantic telephone diplomacy to try to ensure that the vote on the transfer of policing powers from London to Belfast gains all-party support.
Barring a last-minute dramatic twist, that won’t happen. The Ulster Unionists will say “no”.
However, this will not scupper the deal. If the Democratic Unionists vote “yes” - and all the indications so far are that they will - the motion will be passed.
So why all the fuss It seems there are fears that the deal could eventually collapse without all-party support.
Policing and justice: Key points
Reaction: Policing and justice
UUP leader Sir Reg Empey said later: "We’re not prepared to be blackmailed, we’re not prepared to be bullied. We’ve been around a long time.
“Our history is our strength. And we are prepared to go forward and look to the future. But not under the cosh of all this blackmail and bullying.”
The DUP and Sinn Fein have enough assembly members to ensure the vote has the necessary cross-community support to be passed.
Disagreement on the timing of the devolution of the justice powers had threatened to collapse Northern Ireland’s power-sharing administration.
However, Northern Ireland’s two main parties managed to reach a deal which, if the powers are devolved as expected, will see a justice minister elected.
The Hillsborough Agreement allows for the first and deputy first ministers to identify a candidate who would command cross-community support in the assembly.
Alliance leader David Ford is favourite to take the post.
The SDLP’s Alban Maginness is the only other candidate to have been put forward for the job.
The Ulster Unionists and the SDLP have insisted Alliance has no right to the post under the d’Hondt system for selecting ministers, which was agreed in the 1998 Good Friday Agreement.
The UUP also said they could not back the Hillsborough deal on policing and justice because it failed to address matters such as education, parading and “the dysfunctional nature of the current executive”.
It also suggests that 70% of unionists favour Northern Ireland politicians being in charge of policing issues, compared to 83% of nationalists.