The announcement by the party's junior minister Gerry Kelly ends nearly two weeks of round-the-clock negotiations.
The outcome now depends on the reaction of the Democratic Unionist Party.
The DUP and Sinn Féin have been deadlocked on the issue of transferring policing and justice powers from Westminster to Stormont, while they have also debated a new system for overseeing loyal order parades.
Mr Kelly said: 'The negotiations have come to a conclusion.
'We believe that it is a positive conclusion and we believe that it is the basis on which to move forward.'
It has already been widely reported that the unionist party was divided on proposals for a deal presented to members in a private meeting on Monday.
DUP leader Peter Robinson is expected to address his Assembly colleagues as the focus now shifts to whether his party can sign up to the agreement.
The two parties have been involved in ten days of discussions at Hillsborough Castle, Co Down, along with representatives of the Irish and British governments.
Earlier today, Minister for Foreign Affairs Micheál Martin said he believed a positive announcement was in the pipeline.
Sinn Féin Deputy First Minister Martin McGuinness is poised to brief members of his party's officer board on the deal.
