The Irish and British governments may be forced to extend Monday's deadline for a response to their "take it or leave it" proposals to try to break the deadlock threatening the future of the Northern Ireland peace process.
All sides have been asked to make a decision by then but Ulster Unionists tonight said it would be Tuesday at the earliest before they make a final assessment.
At the same time, Sinn Féin hinted it may need more time.
An Ulster Unionist spokesman confirmed that the party was not expected to meet the governments' deadline of Monday before making a response.
Party officers are due to meet on Monday night to discuss the package, while Assembly members will make their views known on Tuesday.
A party spokesman said: "Frankly the governments kept us waiting a long time and it will not hurt them to wait a day or two longer.
"We are clearly now waiting to see what the republican movement does in terms of the fourth part of the package.
"Our emphasis is on seeing them fulfilling their obligations and commitments."
Meanwhile a Sinn Féin delegation is to meet Northern Ireland Secretary Dr John Reid to discuss policing reforms as pressure tonight intensified on the IRA to move towards disarmament.
The Irish and British governments expect the IRA to make a statement of their intentions ahead of the final assessment from the parties.
A delegation of republicans will meet Dr Reid at Hillsborough Castle tomorrow.
Earlier today after a meeting of the party's ruling executive in Castlebellingham, Co Louth, he welcomed what he described as the recognition by the two governments that full implementation of the Belfast Agreement had not yet been achieved.
"I am calling for the two governments to publicise immediately the details of what they are proposing.
"This includes the revised implementation plan on policing, plus the legislative amendments to the Policing Act and the implementation of a plan to deliver a fair and impartial system of justice."
It is feared that this will cause slippage to Monday's deadline date as the criminal justice review was not due for publication until the end of this month.
The Sinn Féin president was speaking as the Secretary of State held separate talks with the other pro-Agreement parties today to brief them on the contents of the policing implementation plan.
Ulster Unionists are believed to be extremely unhappy at many of the main proposals continued in the 80 page document.
Acting First Minister Sir Reg Empey, who led the UUP delegation, said that sweeping reform of the RUC was inconceivable in the present climate of violence.
"The test for all of this is whether we have an effective and efficient police service for Northern Ireland.
"In view of what is happening in Northern Ireland at the present time, talk of disbanding the Police Reserve is an absolute nonsense," he said.
It is understood that the UUP delegation questioned Dr Reid and his officials closely on whether the implementation package would weaken the operational effectiveness of the police service.
Sources have confirmed that the plan includes proposals such as the phasing out of the fulltime RUC reserve, the closure of Gough Barracks, in County Armagh and the restructuring of Special Branch.
However, the British government stressed that the reforms were conditional on the IRA agreeing to begin a process of disarmament.
The document also includes:
- Measures to strip the new police service of Crown emblems including the removal of the Union flag from police stations.
- Increased powers for the police ombudsman and for the new policing board to launch inquiries.
- The appointment of former paramilitaries on district policing partnerships.
- The phasing out of the use of plastic bullets as a method of quelling riots.
- Legislation to enable the lateral entry of members of the Garda into the new police service.
After his meeting with the Secretary of State, SDLP leader Mr John Hume would not commit his party to joining the new Police Board.
His party was seeking clarification from Dr Reid on a range of issues including policing, criminal justice and normalisation.
"We are now considering the matter from our discussions today and we will be continuing to consult with our party colleagues on the joint proposals," he said.
An SDLP spokeswoman told reporters that the party would give its definitive response to the package on Monday.
PA