An American cardinal has said that Islam "wants to govern the world" and is not like other religions such as Christianity and Judaism.
Cardinal Raymond Burke, a Rome-based prelate, said he was not seeking to be "disrespectful" to Islam or to "generate hostility", adding that Muslims "are lovely people" and can speak "in a very peaceful manner about questions of religion."
But the Cardinal also made controversial remarks to the Religion News Service to promote his new book, Hope for the World: To Unite All Things in Christ, an extended interview with a French journalist.
The cardinal, known for his conservative views on the reform agenda of Pope Francis, women in the Church, abortion and homosexuality, said that Islam is "fundamentally a form of government" and that Americans must reassert "the Christian origin of our own nation".
He criticised Catholic leaders who tend "to simply think that Islam is a religion like the Catholic faith or the Jewish faith," adding: "That simply is not objectively the case".
The Cardinal claimed that "when they (Muslims) become the majority in any country they have the duty to submit the whole population to Shariah," referring to Islamic law.
He went on: "(My) point is this: When they [Muslims) become a majority in any country then they have the religious obligation to govern that country. If that's what the citizens of a nation want, well, then, they should just allow this to go on. But if that's not what they want, then they have to find a way to deal with it."
The comments come after the senior Republican and former Speaker of the House of Representatives Newt Gingrich said that anyone found to be of "Muslim background" who supported Sharia law should be "deported" from the US.
The cardinal, who is a canon lawyer and was head of the Vatican's court system before Pope Francis named him chaplain of the Knights of Malta, controversially claimed that in some European cities with Muslim populations "there are little Muslim states" that are effectively "no-go zones" for government authorities.
He added: "This is the way things are to go... And if you do understand that and you are not at peace with the idea of being forcibly under an Islamic government, then you have reason to be afraid."
Asked how the West should respond, he said: "I think the appropriate response is to be firm about the Christian origin of our own nation, and certainly in Europe, and the Christian foundations of the government, and to fortify those... We have to say no, our country is not free to become a Muslim state."
In his book, Cardinal Burke says that "the (Catholic) Church really should be afraid of" Islam.