The agreement was reached between the British and Irish governments as well as eight northern Ireland political parties or groups. Three were representative of unionism: the Ulster Unionist Party, which had led unionism in Ulster since the early 20th century, and two small parties linked to loyalist paramilitaries, the Progressive Unionist Party (linked to the Ulster Volunteer Force (UVF) and the Ulster Democratic Party (the political wing of the Ulster Defence Association (UDA). Two of them have been widely described as nationalists: the Social Democratic and Labour Party and Sinn Féin, the Republican party affiliated with the Provisional Republican Army.   Apart from these rival traditions, there were two other assemblies, the Inter-Community Alliance Party and the Northern Ireland Women`s Coalition. There was also the Labour coalition. U.S. Senator George J. Mitchell was sent by U.S. President Bill Clinton to chair the talks between parties and groups.  Participants in the agreement were composed of two sovereign states (the United Kingdom and the Republic of Ireland), with armed forces and police forces involved in the riots. Two political parties, Sinn Féin and the Progressive Unionist Party (PUP), were linked to paramilitary organisations: the IRA (Commissional Irish Republican Army) and the Ulster Volunteer Force (UVF). The Ulster Democratic Party (UDP), associated with the Ulster Defence Association (UDA), had withdrawn from the talks three months earlier. The main themes addressed by Sunningdale and dealt with in the Belfast Agreement are the principle of self-determination, the recognition of the two national identities, intergovernmental cooperation between the British and Ireland and legal procedures for compulsory power-sharing, such as inter-community voting and the D`Hondt system for appointing ministers to the executive.
  Former IRA member and journalist Tommy McKearney says the main difference is the British government`s intention to negotiate a comprehensive agreement including the IRA and the most intransigent unionists.  With regard to the right to self-determination, two qualifications are recorded by the writer Austen Morgan. First, the transfer of territory from one state to another must be done through an international agreement between the British and Irish governments. Second, the population of Northern Ireland can no longer be alone in united Ireland; They need not only the Irish government, but also the people of their neighbouring country, Ireland, to support unity.