(CNN) -- Some former members of the Irish Republican Army -- "small in number" but "ruthless" -- are trying to undermine the agreement that ended 30 years of deadly violence in Northern Ireland, a former deputy director of the CIA said.
Richard Kerr, who is now a member of the Independent Monitoring Commission (IMC) that tracks paramilitary groups in the British province, told CNN's Christiane Amanpour on Wednesday that members of the so-called "Real IRA" and other breakaway groups are trying to sow disorder by targeting police officers and soldiers in Northern Ireland.
The gunmen, blamed for the deaths of two soldiers and a policeman in March, are out to thwart the 1998 Good Friday agreement that ended three decades of violence that claimed more than 3,500 lives, Kerr said.
But Kerr, who was deputy director of the CIA between 1989 and 1992, said the gunmen are unlikely to undermine the peace agreement. "They are small in number. If you were talking about 100 people, I think you would be in the neighborhood, maybe."
They are probably "hangers-on" with a strong hatred of the British who may have some local support but do not have the backing of their community in any significant way, he said.
His organization, the IMC, last month published a report saying some dissident Irish republicans are "extremely active and dangerous." The report came out in the same month that militants tried and failed to blow up the police reform headquarters in Belfast. There also are concerns among security analysts that the militants could launch attacks on the British mainland.
A leading authority on the conflict, Lord Paul Bew, a professor of Irish history at Queen's University in Belfast, Northern Ireland, told Amanpour the recent attacks come at a time when the nationalist Sinn Fein party, which has close links with former IRA members, is struggling to sell its political strategy.
Sinn Fein is the second largest party in Northern Ireland's Assembly and has four ministerial posts in the power-sharing executive that governs the province under the terms of the Good Friday agreement.
"The Good Friday agreement is not delivering on rapid progress towards Irish unity, which many people in Sinn Fein expected it would do, and many of their voters expected it would do," Bew added.
"It was quite commonly said within that community that 2016, the 100th anniversary of the Easter rising of 1916, would be the date for Irish unity."
Sinn Fein is also locked in a bitter dispute with its main partner in the power-sharing executive, the Democratic Unionist Party (DUP), over whether London should grant Northern Ireland more authority over the police, the criminal justice system and prisons.
The DUP is blocking efforts to transfer those powers to Belfast, Bew said. "The great fear of the unionist right is a republican campaign of violence on the streets while you have republicans also in government exercising power in sensitive areas such as policing and justice," he added.
But Bew, a member of the British House of Lords, said that while the dispute has symbolic importance, it does not matter so much in practical terms because Northern Ireland already has some control over policing at a local level, and the British maintain a large intelligence operation in Northern Ireland.