In this Year of Faith, we have been asked to reexamine the documents of the Second Vatican Council. One of these documents is called Unitatis Redintegratio, commonly called the "Decree on Ecumenism" in English.
The first paragraph of this conciliar document clearly and unambiguously expresses the sentiments of the Catholic Church in regard to Christian unity:
The restoration of unity among all Christians is one of the principal concerns of the Second Vatican Council. Christ the Lord founded one Church and one Church only. However, many Christian communions present themselves to men as the true inheritors of Jesus Christ; all indeed profess to be followers of the Lord but differ in mind and go their different ways, as if Christ Himself were divided. Such division openly contradicts the will of Christ, scandalizes the world, and damages the holy cause of preaching the Gospel to every creature. The full text is here - http://ow.ly/gIBS5
Recently, Pope Benedict XVI spoke directly and clearly about Christian unity (20 Jan 2013) saying:
One of the most serious sins that disfigures the face of the Church is against its visible unity, especially the historical divisions the have separated Christians that haven't yet been overcome.
It's a moment always welcome to believers and communities, which awakens in all the desire and spirit of commitment to full communion.
The Pope will close the week of prayer for Christian unity 2013 by presiding at vespers in the Basilica of St. Paul Outside the Walls alongside representatives of other churches and communities.