The Ulster Unionists have accused the NI Secretary of State of "political and emotional blackmail" ahead of tomorrow's vote on the transfer of justice powers.

Shaun Woodward said today that the vote would be the most important in Northern Ireland history.

He also urged the Ulster Unionists to vote in favor 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.

Mr Woodward said transferring justice powers tomorrow would send an important message to those responsible for his death and dissident republicans in general.

But Mr Kennedy said the Secretary of State was guilty of "political and emotional blackmail" and called on him to consider his position.

The UUP has been refusing to endorse the Hillsborough Agreement, insisting that matters such as education, parading and "the dysfunctional nature of the current Executive" must be addressed.

"You wouldn't buy a machine that already malfunctioned and overload it then with more than it could cope with," UUP MLA David McNarry said.

"They have enough votes, Sinn Fein and the DUP to get us through this and this is all just hype, it's just fabrication."

"We're doing what we've always done, we're responsible, and actually it was us who put devolution on the map."

In a statement at the weekend, two US congressional groups urged the UUP to "take a risk for peace".

They also called on UK Conservative Party leader David Cameron to use his influence with the party.

Ulster Unionists have said their final decision will be made this evening.

The latest appeal follows a weekend of telephone diplomacy in which US Secretary Hillary Clinton phoned Ulster Unionist leader Sir Reg Empey in an effort to move the situation forward.

They talked for about 15 minutes. Afterwards Ulster Unionist sources said Mrs Clinton did not try to strong-arm them into changing their position.

Mrs Clinton also spent 15 minutes talking to Deputy First Minister Martin McGuinness from Sinn Fein.

The US statement issued by the Friends of Ireland in the United States House of Representatives and the Ad Hoc Committee on Irish Affairs expressed "deep disappointment" at the Ulster Unionist stance.

The five congressmen who signed it - Richard E Neal, Peter King, Joseph Crowley, Chris Smith and Tim Murphy - said this was a "crucial and defining moment in the peace process".

Meanwhile, the Ulster Unionists are to ask for figures on the cost of an opinion poll commissioned by the Northern Ireland Office suggesting 68% of people in Northern Ireland want to see local politicians taking responsibility for policing and justice.

A total of 1,000 people were interviewed for the poll on Friday and Saturday.

A clear majority - 68% - told the pollsters that local ministers should make decisions on policing whilst only 14% wanted the powers to remain with direct rule ministers.

A similar percentage backed the Hillsborough deal negotiated last month.