Republican presidential frontrunner Donald Trump called Monday for “a total and complete shutdown of Muslims entering the United States until our country’s representatives can figure out what is going on.”

In the most dramatic reaction to date from a presidential contender to recent terrorist attacks, Trump argued that anyone belonging to the faith should be considered a potential threat. The ban would presumably apply to immigrants, tourists and business travelers. It would also include Muslim-American citizens outside of the country who are looking to return, Trump spokeswoman Hope Hicks confirmed to The Hill in an email.

“Without looking at the various polling data, it is obvious to anybody the hatred is beyond comprehension,” Trump said in the statement. “Where this hatred comes from and why we will have to determine. Until we are able to determine and understand this problem and the dangerous threat it poses, our country cannot be the victims of horrendous attacks by people that believe only in Jihad, and have no sense of reason or respect for human life. If I win the election for President, we are going to Make America Great Again.”

The email cites a 2015 study by the Center for Security Policy, a group that advocates a more aggressive response to Islamic radicalism, that found 25% of Muslims living in the United States agreed violence against Americans was justified as part of the global jihad, and 51% polled agreed that Muslims in America should have the choice of being governed according to Shariah law. The survey, which was not published with a margin of error, was completed “online” under procedures that were undisclosed had a sample of 600 self-identified Muslims.

The director of the Center for Security Policy, Frank Gaffney, recently stopped appearing on panels for the Conservative Political Action Conference, one of the largest annual gatherings of conservative activists, because he argued the group had been under the “malign influence” of leaders with “involvement in the Muslim Brotherhood.” One of the leaders Gaffney targeted was Americans for Tax Reform President Grover Norquist, who has no personal involvement with the brotherhood.

The White House promptly responded to Trump’s call. “We should be making it harder for ISIL to portray this as a war between the United States and Islam, not easier,” said Ben Rhodes, a deputy national security adviser to President Obama. “It’s totally contrary to our values as Americans. . . . It’s also contrary to our security.”

Trump is not the first GOP candidate to suggest restricting Muslim immigration, though he is certainly the first to call for a “complete shutdown.” Kentucky Sen. Rand Paul, a frequent sparring partner of Trump’s, called for restricted immigration, including a denial of visas and refugee status, from 34 mostly Muslim countries, including Mali, Turkey and Morocco. Former Florida Gov. Jeb Bush and Texas Sen. Ted Cruz have suggested only allowing in Christian refugees from Syria.

In response to Trump’s press release, Democratic underdog candidate Martin O’Malley tweeted a rapid condemnation of Trump. “He is running for President as a fascist demagogue,” the Tweet read.

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Write to Tessa Berenson at tessa.berenson@time.com.