Sir Reg Empey said aspects of the agreement needed to be clarified
Ulster Unionist Party leader Sir Reg Empey has said he will not be "rushed into any decision" about the deal reached by the DUP and Sinn Fein.
Sir Reg said his party must examine the document "on its merits".
"As I have repeatedly stated the UUP has not been involved in any of the negotiations which led to this Agreement," he said.
Sir Reg said his party would seek clarification from Prime Minister Gordon Brown about the deal.
"Sinn Fein constantly talk about equality and inclusion, however they have consistently sought and achieved the exclusion of two Executive parties," he continued.
"I must make it clear - we will not be rushed into any decisions - the DUP and Sinn Fein have taken 120 hours to negotiate this document so we will take as long as it takes to come to our conclusions."
Throughout the talks between the DUP and Sinn Fein at Hillsborough Castle, the Ulster Unionists voiced their frustration at being excluded.
Sir Reg said he only received the document at 1100 GMT on Friday and that his party should have been told what the agreement contained before it was made public.
Ulster Unionist support for the agreement is seen as crucial, because the DUP has long insisted the wider unionist community needed confidence before a deal could be reached on devolving policing and justice powers.
Sir Reg said it was "unfortunate" that he had not been asked whether he would take on the role envisaged for him in the agreement as co-chair along with the SDLP's Margaret Ritchie of a working group to examine ways to improve how the power-sharing cabinet operates.
"I think that indicates the distance that has been placed between ourselves and the rest of the process," he said.
It also emerged in recent weeks that the Orange Order convened
secret unity talks
between the DUP and UUP in early December.
The parties discussed the possibility of electoral pacts and forming a unionist bloc at Stormont.
However, the Ulster Unionists have ruled out any merger with the DUP and restated their commitment to their electoral pact with the Conservative Party, where they will field joint candidates under the banner Ulster Conservatives and Unionists - New Force (UCUNF).
Conservative leader David Cameron said on Friday: "We welcome the fact that an agreement has been reached between the Democratic Unionists and Sinn Fein, and we support the determination of the British and Irish governments in helping to bring this about.
"We hope this leads to the completion of devolution and the re-establishment of political stability in Northern Ireland."