Donald Trump “would certainly implement” a database system tracking Muslims in the United States, the Republican front-runner told NBC News on Thursday night.

“I would certainly implement that. Absolutely,” Trump said in Newton, Iowa, in between campaign town halls.

“There should be a lot of systems, beyond databases,” he added. “We should have a lot of systems.”

When asked whether Muslims would be legally obligated to sign into the database, Trump responded, “They have to be — they have to be.”