Barack Obama's controversial Deferred Action for Childhood Arrivals (DACA) allowed children who came to the U.S. illegally to stay, but the program might come to an end as soon as the Trump administration considers its choices.

President Donald Trump is likely to end the program or let it expire in over the course of two years, according to government officials who spoke to NBC News. They said it is unclear which option he will choose but that Attorney General Jeff Sessions has long opposed DACA, and Thursday he discussed the program with White House officials.

DACA allows those who were brought to the U.S. at the age of 16 or younger by 2007, or overstayed their visas in the same timeframe, to have deferred status to live in the U.S. rather than return to their home country.

Press Secretary Sarah Huckabee Sanders said the program "continues to be under review," even though Trump made a campaign promise to revoke it. Opponents of DACA have said the program is overly broad and constitutes a legally dubious rewriting of existing law.

"The president should end a program that is illegal, overbroad, and likely to lead to a more extensive amnesty," Steven Camerota, director of research at the Center for Immigration Studies, wrote.

Obama himself said that he did not have the authority to change immigration enforcement in an interview with Univision, which critics cite as evidence that DACA went beyond his presidential authority.

"There are enough laws on the books by Congress that are very clear in terms of how we have to enforce our immigration system that for me to simply through executive order ignore those congressional mandates would not conform with my appropriate role as president," Obama said in 2011, the year before he put DACA into effect.

He has since urged his successor to hesitate before ending DACA.

"The notion that we would just arbitrarily or because of politics punish those kids, when they didn't do something themselves … would merit my speaking out," Obama said.

Immigration advocates have mobilized to argue against rescinding DACA, however, demonstrating outside the White House and defending the value of the program.

"It would be a grave moral and legal error," Vanita Gupta said.

Gupta is the former head of Obama's civil rights division of the Justice Department and now serves as director of the Leadership Conference on Human Rights.

"Killing the DACA program as the Trump administration's first post-Charlottesville move would be absolutely shameful," Gupta added. "We must not allow the hate violence that we saw on the streets of Charlottesville to become the guiding force for policy making."

Greisa Martínez Rosas is a DACA recipient and the director of advocacy and policy at the pro-immigration group United We Dream, and she said Trump would be irresponsible to end DACA.

"We are ready to ensure that Donald Trump does not throw our lives to Congress like a hot potato,"Martínez Rosas said. "Donald Trump has the ability to keep the program in place and we will force him to do that—he awakened a sleeping giant and we will not go back to sleep."