Republican presidential nominee Donald Trump reiterated on Monday that he would keep out certain immigrants and refugees ― especially Muslims ― in response to a bombing in New York on Saturday that authorities blame on a naturalized U.S. citizen.

“You can’t have vetting if you don’t look at ideology,” Trump said at an event in Fort Myers, Florida, before accusing his Democratic opponent of being weak on the threat from terrorism. “Hillary Clinton refuses to consider an applicant’s worldview and thus their likelihood of being recruited into the terror cause at some later date, which is going to happen in many, many cases.”

It was an argument not just for banning terrorists, but also those who could become terrorists ― a murky category when applied to the New York bombing, allegedly by a man who came to the U.S. as a child more than two decades ago.

The suspect, 28-year-old Ahmad Khan Rahami, reportedly immigrated to the U.S. from Afghanistan in 1995 as the son of an asylum seeker. That means the attack doesn’t serve as an easy example of weaknesses in the current vetting system for immigrants. Rahami came to the U.S. before immigration policy changes made after the Sept. 11, 2001, terrorist attacks, and arrived here as a child. Nor can he be used as proof of a risk from refugees, because he wasn’t one.

Asylum and refugee status are often confused, because they both apply to individuals who say they are persecuted in their native countries. But they’re not the same. In asylum cases, the individual comes to the U.S. and then applies. Refugees are screened outside the U.S. and then resettle here. By the time a refugee arrives on U.S. soil, the person has already undergone security checks.

While U.S. intelligence officials have expressed concerns about vetting Syrian refugees, citing instability in the country, they haven’t said screening is impossible, and it certainly isn’t non-existent. FBI Director James Comey said last year that it was impossible to guarantee a risk-free process, but also that officials “are much better” at vetting than they had been. All refugees are screened in processes that include in-person interviews and database checks, and Syrians go through additional steps, according to the administration.

Of the 10,000 Syrian refugees welcomed to the U.S. in the last year, about 60 percent were minors, according to the State Department.

The rate of terrorism by people who entered the U.S. as refugees is low. The Cato Institute reported 20 instances of refugees convicted of planning or committing a terrorist attack in the U.S. from 1975 to the end of 2015, of the 3.25 million refugees admitted to the country in that period. The author of the Cato report, Alex Nowrasteh, wrote that “the chance of an American being murdered in a terrorist attack caused by a refugee is 1 in 3.64 billion per year.” Only four of the more than 700,000 people admitted as asylum-seekers in the same period were convicted of planning or committing terrorism on U.S. soil, according to report, which came out this month.

Rahami is Muslim, which fits more neatly into Trump’s arguments. The GOP nominee last year promised a “total and complete shutdown of Muslims entering the United States.”

Trump has since shifted to a ban on people from countries “compromised by terrorism” rather than a ban on all Muslims, but his policies clearly target the faith and Muslim-majority countries. He said in July that “you could say it’s an expansion” of his initial Muslim ban. Trump said in August that there should be “extreme, extreme vetting” of those who want to enter the United States, using an ideological test that would include questions about Sharia law.

On Monday, Trump said again that the U.S. “should temporarily suspend immigration entirely from regions where safe and adequate screening cannot occur.”

Trump also accused Clinton of having “the most open borders policy of anyone ever to seek the presidency.”

Clinton doesn’t support an open-borders policy ― nor does President Barack Obama ― even though she does not share Trump’s call for a wall between the U.S. and Mexico. She called on Monday for “tough vetting,” although she has not reversed her position on admitting more Syrian refugees.

“I am absolutely in favor of and have long been an advocate for tough vetting,” Clinton said at a press conference. She added that she wants “a better visa system,” noting that the 9/11 attackers came to the U.S. on student, tourist and business visas.

“These were not refugees who got into airplanes and attacked our city and our country,” Clinton said. “So let’s not get diverted and distracted by the kind of campaign rhetoric we hear coming from the other side.”

Editor’s note: Donald Trump regularly incites political violence and is a serial liar, rampant xenophobe, racist, misogynist and birther who has repeatedly pledged to ban all Muslims — 1.6 billion members of an entire religion — from entering the U.S.