This will be an irrevocable decision and, therefore, it is of the utmost importance that countries fulfil the convergence criteria both in a nominal and a real - namely sustainable - manner before they join the euro area, in accordance with the Treaty.
BIS Review 24/2004  3  Since the signing of the Treaty of Accession in April 2003, the dialogue among central bankers from the current and new Member States has been further strengthened to help the national central banks of the new Member States to prepare for accession to the ESCB. Indeed, cooperation among central banks has played an important role in this regard.