101 I therefore exhort my Brothers in the Episcopate to be especially mindful of this commitment. The two Codes of Canon Law include among the responsibilities of the Bishop that of promoting the unity of all Christians by supporting all activities or initiatives undertaken for this purpose, in the awareness that the Church has this obligation from the will of Christ himself. This is part of the episcopal mission and it is a duty which derives directly from fidelity to Christ, the Shepherd of the Church. Indeed all the faithful are asked by the Spirit of God to do everything possible to strengthen the bonds of communion between all Christians and to increase cooperation between Christ's followers: "Concern for restoring unity pertains to the whole Church, faithful and clergy alike. It extends to everyone according to the potential of each".
Source: Ut Unum Sint (Vatican.va)