Christians assisting migrants should love them "without hidden intentions" and not try to convert them, says a leading cardinal at the Vatican.

Cardinal Gerhard Müller said that proselytism "is practically a manipulation of the conscience" and that the mission of the Church is to help mankind relate to and love those escaping war and persecution, Catholic News Service reports.

The cardinal  was speaking at an international conference at the Vatican organized to reflect on Pope Benedict XVI's first encyclical, Deus Caritas Est, on charity ("God Is Love") and the relevance of the Christian perspective of love in today's world.

Müller who carries the title of the prefect of the Congregation for the Doctrine of the Faith, asserted that the Church must assist with more than just material needs.

"The mission of the church is to give witness to Jesus Christ. It would be a way of despising someone if I said: 'You only have material needs,'" Cardinal Müller said Feb. 25 at an international conference held at the Vatican.

Jesus' commandment to love one's neighor, he said, is a call for Christians to manifest God's love to others, particularly through works of charity. However, in addressing the needs of migrants, Christians are called to help "without hidden intentions."

"We must not use the charity we practice and transform it into an instrument of proselytism," he said.

"An expert Christian knows when it is time to speak about God and when it is best to keep quiet. Sometimes a silent witness is the best witness of the love of God."

The cardinal noted that in his native Germany, which has received tens of thousands of migrants from Muslim-majority countries, the authentic witness of love through charity has caused migrants to inquire about the Christian faith without imposing one's beliefs on them.

"There are among these migrants, the majority of whom are Muslim, who ask, 'Why are Christians - and not our fellow Muslims - helping us?' The love of neighbor is a starting point to the love of God because God, through Jesus Christ, is the cause and essence of our love toward our neighbor," the cardinal said.

Müller noted that the commitment of charity and love toward one's neighbor should be sustained by prayer or risks becoming "blind activism and a fanatical desire to reform the world."

Using religious differences as a pretext to exclude others is contrary to faith because "God does not exclude anyone," the cardinal added. Excluding others "builds a wall that separates us from God; this is the original sin."

Cardinal Muller said that instead, the church's mission is "to help overcome these walls" that only serve to exclude humankind "from both God and neighbor."

Since late 2014 a working group of representatives from the Catholic Church (Pontifical Council for Promoting Christian Unity), the Pentecostal World Fellowship, the World Council of Churches, and the World Evangelical Alliance as well as members of the Global Christian Forum has agreed on a series of aims and approaches for tackling concerns associated with mission and proselytism.