ROME — Marking the 25th anniversary of St. John Paul II’s encyclical on Christian unity, Pope Francis said he shares “the healthy impatience” of those who think more can and should be done, but he also insisted that Christians must be grateful for the progress made.

“Many steps have been taken in these decades to heal the wounds of centuries and millennia,” Pope Francis said in a letter to Cardinal Kurt Koch, president of the Pontifical Council for Promoting Christian Unity.

The letter was released by the Vatican May 25, the anniversary of John Paul’s 1995 encyclical, “Ut Unum Sint,” Latin for “that they may be one.”

In the encyclical, John Paul: Reaffirmed the Catholic Church’s “irrevocable” commitment to working and praying for Christian unity; highlighted how Christians of all denominations already are united in the experience of martyrdom; called for efforts to promote a “healing of historical memories” and mutual forgiveness; asked other Christians to join a dialogue on the ministry of the bishop of Rome — the pope — in a united Christianity; and insisted that dialogue is not a negotiation, but a sharing of the gifts God has given each community.

Over the past 25 years, Pope Francis said, “mutual knowledge and esteem have grown and helped to overcome deeply rooted prejudices” and “theological dialogue and the dialogue of charity have developed, as well as various forms of cooperation in the dialogue of life, at both the pastoral and cultural level.”

The pope also used his letter to Koch to greet the heads of the Christian churches and “all our brothers and sisters of every Christian tradition who are our companions on this journey.”

“Like the disciples of Emmaus, may we experience the presence of the risen Christ who walks at our side and explains the Scriptures to us,” the pope wrote. “May we recognize him in the breaking of the bread, as we await the day when we shall share the Eucharistic table together.”

Francis thanked the staff of the pontifical council for their work on behalf of the church and thanked the council for preparing an “Ecumenical Vademecum for Bishops,” which will offer practical advice and encouragement to bishops in fulfilling their obligation to promote Christian unity on a local level. The document is expected to be published in the fall.

“On the path that leads to full communion, it is important to keep in mind the progress already made, but it is equally important to scan the horizon and ask,” as John Paul did, “Quanta est nobis via?” (How much further must we travel?), Francis said.

He did not answer the question, but Francis insisted “unity is not chiefly the result of our activity, but a gift of the Holy Spirit,” which is why Christians must pray for the gift of unity.

“With confidence, then, let us ask the Holy Spirit to guide our steps and to enable everyone to hear the call to work for the cause of ecumenism with renewed vigor,” he wrote. “May the Spirit inspire new prophetic gestures and strengthen fraternal charity among all Christ’s disciples ‘that the world may believe’ to the ever greater praise of our Father in heaven.”