President Donald Trump is “likely” to end the Deferred Action for Childhood Arrivals, or DACA, program, an initiative started by former President Barack Obama that lets young undocumented immigrants who were brought to the U.S. illegally when they were minors stay in the country, NBC News reported Friday.

It’s unclear whether Trump would immediately end DACA or gradually let it expire, NBC News reported. But either way, ending the program could impact up to 1 million undocumented immigrants.

Created in 2012, DACA allows undocumented immigrants who were 16 or younger when they were brought to the U.S. stay in the country so long as they haven’t committed crimes. The program also applies to undocumented immigrants who came to the U.S. legally, but stayed in the U.S. after their visas expired. (A full list of criteria to qualify for DACA is available here.)

Trump has waffled on what he wanted to do with DACA. During the campaign, he said he would end the program. However in April, he suggested that those in the DACA program — known as “dreamers” — would not be directly impacted.

‘‘Here is what they can hear: The ‘dreamers’ should rest easy,’’ Trump said at the time. ‘‘OK? I’ll give you that. The ‘dreamers’ should rest easy.’’