The son of Billy Graham who now heads his father's evangelistic organisation has described Islam as a "religion of war" and urged Christians to attempt to convert Muslims to their own faith.

Franklin Graham, the fourth of Billy Graham's five children, said he had not softened his stance since he controversially referred to Islam as a "very wicked and evil religion" in the wake of the 9/11 attacks in 2001 that brought down the World Trade Centre in New York.

More recently, he criticised The Episcopal Church's National Cathedral in Washington for permitting its first Muslim prayer service. On his Facebook page he wrote: "It's sad to see a church open its doors to the worship of anything other than the One True God of the Bible who sent His Son, the Lord Jesus Christ, to earth to save us from our sins."

His views contrast with those of the Pope, who on his recent three-day visit to Turkey was moved to pray alongside Grand Mufti Rahmi Yaran in Istanbul's Blue Mosque. Beside working to build better relations with Muslims, Pope Francis is also reaching out to evangelicals, a move which came about because of his friendship with the late Bishop Tony Palmer, a charismatic of the Communion of Evangelical Episcopal Churches.

Franklin Graham told Christian Today that his own views on Islam remained the same as in 2001.

"I have not changed my opinion at all." He said he looked at Islamic State, at the Taliban and Boko Haram and thought: "This is Islam. It has not been hijacked by radicals. This is the faith, this is the religion. It is what it is. It speaks for itself."

He added: "I think it is very important that we do all that we can to try to share God's love with Muslims because they have no hope outside of dying in Jihad. I want them to know, you do not have to die for God. God died for us. He sent His Son to die for us. We do not have to kill ourselves to please God. I want them to know that they can have eternal life."

Islam itself had not changed at all in 1500 years, he added. "It is the same. It is a religion of war."

He said he was "sad" that Muslims in the Washington cathedral had "turned their back on the Cross" to worship "another God". Graham said: "The God of Islam is not the same God of the Judaeo-Christian faith. "The God that we worship in Christianity is a God that has a Son. To Islam, that is blasphemy, to say that God has a son. Therefore, they do not worship the God that we worship."

Franklin Graham has made an international impact as head of Samaritan's Purse, a charity whose international relief projects include Operation Christmas Child, where churches and individuals fill shoeboxes with gifts that are donated to children in more than 100 countries.

Graham recalled that he first got involved in Operation Christmas Child when he was approached from the UK one summer about sending gifts to children in Europe. Graham forgot about it, until he received another call that December, asking how many shoeboxes he had collected. "I told him I am still working on it, give me another week. God began to work in people's hearts as people began to pack those boxes. We would have been happy with two or three thousand but we got 11,000 in that first year." The operation took off, he said, after it was made explicitly Christian, and moved from being mainly in schools to being church-based.

He began helping his father out with the Billy Graham Evangelistic Association in 1989. He became the CEO in 2000 and president in 2002.

Asked if he ever felt his own identity had been sacrificed to that of the charismatic Billy Graham, Franklin said: "I have never really tried to forge my own identity. As followers of Jesus Christ, we ought to forge our identity in Him. I want to take my life and the time I have on this earth to try to tell others about Jesus, that Jesus Christ is God's son who took our sins to the Cross and shed His blood for our sins. If we are willing to put faith and trust in Him, God will forgive our sins, heal our hurts and give us eternal life."

He said that when his father reached his 80s, he did not have the strength to remain in charge. Franklin was already well-established running Samaritan's Purse, as well as preaching and giving a substantial proportion of this time to his father's organisation. His father asked him if he would accept the succession, if the board approved it first.

"I said, Daddy I am here to serve you and whatever you want, I will be happy to do that."

He believes God placed him in that position, and he had a duty to please his heavenly Father as well as his father on earth. It was his role, he believes, to help his father finish the job given him by God and to finish it well. By taking over some of the desk work and the administrative duties, he was therefore helping prolong his father's ministry. "My father has been faithful to the calling that God gave him, that is to preach the Gospel... He has presented Christ to every person that God has put before him."

When his mother Ruth died in 2007, Franklin asked Billy Graham what he would like on his headstone when he went to join her. His father replied: "Just put, Preacher."