Upon accession, the new Member States will join Economic and Monetary Union with the status of "countries with a derogation" and their central banks will become part of the ESCB. At a later stage, the acceding countries' central banks will become part of the Eurosystem, after these countries have fulfilled the convergence criteria for adopting the euro.
A key priority of the ECB is to have in place the necessary technical and institutional infrastructure which will ensure an orderly enlargement of the ESCB and, later on, of the Eurosystem.