A delegation from the Ulster Unionist Party is meeting the Taoiseach and the British Prime Minister in Downing Street this afternoon.
The talks, which will be attended later by Sinn Fein and the SDLP, are trying to resolve issues including decommissioning and police reform.
The ban on Sinn Fein ministers attending cross border meetings is also on the agenda.
Sinn Fein's Gerry Adams says the implementation of the Good Friday Agreement lies with the British Government.
The Ulster Unionist Party says the continuation of the Agreement is at the eleventh hour.