Who used to be Tony Blair's Chief of Staff and a key person in the peace negotiations of Northern Ireland, Jonathan Powell, could not say it more clear:
If you want the dissolution of an armed organization, if you want to move ahead, you must get involved, make compromises and engage in dialogue. That is what we learned in Ireland.
Powell is co-signatory of the declaration of Aiete, pushing for a peace process in the Basque-Spanish conflict, together with former UN Secretary General Kofi Anan, former Norwegian Prime Minister and head of WHO, Gro Harlem Brundtland, former Taoiseach Bertie Arhern, veteran French politician Pierre Joxe and the leader of the Sinn Feinn Gerry Adams.
The declarations were made in a European Parliament conference organized by some MEPs and which gathered some one hundred attendants, many of them political representatives from all around the European Union.
Powell also said in reference to ETA and the Basque National Liberation Movement:
If one advances towards peace so suddenly, one can end up exhausted. Therefore the importance of doubling efforts and moving ahead, so nothing is gone to waste.
He also said that the current lack of a proper peace process can lead to new violence:
Peace is a process not an event. If there is no process, a vacuum is created which can eventually be filled with violence. Therefore a process is needed to reach to a solution and that also applies to Basque Country and to Spain. You can't reach to any agreement if there is no process.
A conflict does not go away just because we wish so. The Government demands the dissolution of ETA but any such organization does not dissolve itself just like that. Even the Police Chief of Northern Ireland told us that negotiation would be necessary to solve the problem. We talked to the IRA...
Other participants also made comments in similar directions.
Source: Gara[es] (all quotes here back-translated from Spanish into English).