Newt Gingrich, a former Republican Speaker of the House, made the comments in the wake of the mass slaughter of at least 84 people in southern French city.
Speaking to Fox News, Mr Gingrich, who has endorsed Donald Trump, has called for any Muslim who believes in Sharia Law to be deported.
He said: “Western civilisation is in a war. We should frankly test every person here who is of a Muslim background, and if they believe in Sharia, they should be deported.
“Sharia is incompatible with Western civilisation.
“Modern Muslims who have given up Sharia, glad to have them as citizen… But we need to be fairly relentless about defining who our enemies are.”