It’s one of Trump’s most controversial policy proposals.

Secretary of State-designate Rex Tillerson testifies on Capitol Hill in Washington, Wednesday, Jan. 11, 2017, at his confirmation hearing before the Senate Foreign Relations Committee. CREDIT: AP Photo/J. Scott Applewhite

Rex Tillerson, President-elect Donald Trump’s pick for Secretary of State, won’t rule out support for Trump’s controversial promise to enforce a national registry to identify American Muslims. In fact, he would consider expanding the registry to “other groups that are threats to the United States” if it can be used as a tool for vetting.

“I would need to have a lot more information around how such an approach would even be constructed,” Tillerson said Wednesday during his Senate confirmation hearing, after Sen. Jeanne Shaheen (D-NH) asked about his support for the registry. “And if it were a tool for vetting, then it probably extends to other people as well, other groups that are threats to the United States. It would require me, much more information to how that would even be approached.”

Sen. Cory Booker (D-NJ) asked Tillerson during the hearing whether he would support reviving NSEERS. “I’m not familiar enough to be able to address it specifically,” Tillerson responded. “I’m happy to get back to you with an answer though.”

Tillerson also told senators at the hearing that he didn’t support a “blanket-type rejection” to restrict travel by Muslims into the United States. But he cautioned, “clearly we have serious challenges to be able to vet people coming into the country.” He further said that a special visa waiver program intended to bring Afghans who help military men and women on the ground into the United States should be more thoroughly examined.

Trump made a campaign promise to create a program that would target people from some “high-risk” countries for “extreme vetting,” especially singling out Muslims from terrorist-prone countries.

Tillerson’s support for the registry clashes with the position taken by Gen. John Kelly — Trump’s choice for Department of Homeland Security Secretary. At Kelly’s confirmation hearing on Tuesday, he distanced himself from the registry, saying that he didn’t think “it’s ever appropriate to focus on something like religion as the only factor.”

Muslims in the United States already know what it’s like to live under law enforcement surveillance. As recent as 2015, the New York City Police Department routinely extended investigations of Muslims without getting the proper authorization. Between 2002 and 2011, the U.S. government enforced the controversial practice of tracking Muslims and members of the South Asian community through the National Security Entry-Exit Registration System (NSEERS). Targeting visitors from 25 countries, 24 of which are majority Arab or Muslim, the program profiled mainly Arab and Muslim male immigrants who were forced to register their biometrics and personal information into a database. They also had to check in with immigration officials. The program was ultimately a failure, and Obama announced last month that he would be ending it.

Trump has called for the revival of the dormant NSEERS program, with advisers saying that he would ban people from countries that have a history of Islamist extremism.

Trump’s Secretary of State nominee won’t rule out a Muslim registry was originally published in ThinkProgress on Medium, where people are continuing the conversation by highlighting and responding to this story.