Does Donald Trump have a plan to prevent homegrown terror attacks?

Asked Wednesday about the recent ISIS-inspired truck attack in Berlin, President-elect Donald Trump appeared to double down on his campaign plans to stop terrorism by temporarily banning immigration from Muslim countries and creating a “registry” of Muslim immigrants already in the United States.

“You know my plans,” he said, when asked by a reporter about the two proposals.

Trump ran on the idea that the United States can prevent terrorism by not letting Muslim immigrants into the country. But as he takes office in January, the president-elect will collide with the reality that the United States’ terrorism problem is very different from that of Germany, which took in about a million primarily Syrian refugees in the space of a few years. America’s problem is homegrown.

Since 9/11, every major terror attack on U.S. soil has been carried out by a legal permanent resident or U.S. citizen. An analysis of the dozens of people prosecuted for plotting ISIS-inspired terror attacks here or seeking to travel to Syria to become foreign fighters shows that 80 percent of the would-be terrorists are U.S. citizens. The vast majority of them are in their early 20s or late teens, and a third converted to Islam from another religion.

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The Obama administration has spent millions of dollars addressing this homegrown threat, steering money into research about how to prevent radicalization and funding law enforcement pilot programs in major cities such as Los Angeles and the Twin Cities to build trust between police and Muslim communities. The administration created a senior role at the Department of Homeland Security (DHS) to coordinate these programs, which are referred to as “countering violent extremism” or CVE. The CVE effort tries to prevent young people from being indoctrinated by radical Islamic extremism online, and also targets other forms of extremism, like white supremacy.

“The sad part is we’re really at the very beginning of understanding what programs to put in place and what programs work,” said Karen Greenberg, director of the Center on National Security at Fordham University School of Law.

The fate of these initiatives under the Trump administration is unclear. Trump has said almost nothing about how to prevent radicalization at home except for saying that Muslim Americans must report to authorities when a member of their community is behaving suspiciously.

Retired Marine Gen. John Kelly, Trump’s pick to lead DHS, said in an interview with NPR last year that ISIS had perverted Islam into a radical doctrine, and that “the vast majority of Muslims are wonderful people, whether they live here in the United States or overseas.” He acknowledged that winning the ideological war against ISIS is “the more difficult, complex part of the problem” than beating the group on the battlefield. “I think we have to steel ourselves for a fairly long war,” Kelly said.

But Kelly did not elaborate on how that ideological war could be won, and it’s unclear whether he supports the Obama administration’s approach to countering homegrown radicalization. He declined an interview through a representative of the Trump transition team.

Republicans are already pressuring DHS to discard the Obama administration’s counterterror approach. House Homeland Security Committee Chairman Michael McCaul, R-Texas, who also sought the DHS chief job, said in a speech earlier this month that the administration should “repeal and replace” President Obama’s “failed, politically correct ‘Countering Violent Extremism’ policies.” McCaul said the programs should be refashioned to explicitly target “radical Islamist terror.”

That approach would likely be supported by Michael Flynn, Trump’s national security adviser. In his 2016 book, “Field of Fight,” Flynn writes that the way to prevent people from being attracted to the ideas of radical Islam is for U.S. politicians to condemn them. Flynn has also made statements that suggest he does not distinguish between adherents of radical Islam and moderate Muslims. Earlier this year, he tweeted that “fear of Muslims is RATIONAL.”

Flynn believes that criticizing the radical strain of the religion would lead to fewer terror attacks.

“Our leaders have to say these people are a threat to the country, and we have to combat them,” said Michael Ledeen, Flynn’s co-writer and a Freedom Scholar at the Foundation for Defense of Democracies. “It will encourage Muslims who don’t like radicalism to come forward and organize and combat the radicals. It will encourage them to cooperate more with law enforcement officials across the country.”

But academics who study CVE programs say that labeling Muslims broadly as extremists erases the goodwill built between these communities and law enforcement. CVE programs are labeled as targeting extremism in general, not just Islamic extremism, in order to gain the support of Muslim communities and show that the government recognizes extremism comes in many forms.

“One of the real difficulties in implementing CVE has been a lot of pushback from Muslim American communities who resent being singled out,” said Stevan Weine, who researches CVE programs and is a professor of psychiatry at the University of Illinois at Chicago. “They are aware that a very large portion of attacks in the U.S. are caused by white supremacists and not Muslim jihadists. They resent the singling out of their community, which they think violates civil liberties and causes stigma and discrimination.”

If the government labels the programs to explicitly focus on Muslims, Weine said they’re likely “not to have the cooperation of the community.” This is a problem, since law enforcement relies on family members and friends to alert them if their loved one shows signs of becoming radicalized.

John Horgan, a psychologist at Georgia State University who studies ISIS’ recruiting tactics, said he fears the emerging field of countering terror recruiting and radicalization could be swept away by the new administration.

“We’ve already made some serious strides in countering terrorism, and we need to do this smart,” Horgan said. “The consequences of not doing this the right way will be profound in ways that I think none of us really understand yet.”