One such group, United We Dream, tweeted back at Mr. Trump Tuesday morning, urging him not to take action against DACA.
The president’s move is also likely to be greeted with skepticism and frustration by many of his most conservative supporters, who had expected that Mr. Trump would put a permanent end to what they view as an illegal abuse of executive authority by former President Barack Obama to grant amnesty to undocumented immigrants.
And it is unclear whether the Republican-controlled Congress will be willing to pass legislative protections for the young, undocumented immigrants. Republicans have repeatedly blocked similar legislation from passage for more than a decade.
Speaker Paul D. Ryan recently suggested that he believes Congress should handle the issue, saying that “this is something that Congress has to fix.”
But more conservative members of Mr. Ryan’s caucus are certain to oppose such moves, supported by loud, anti-immigrant hawks who dominate talk radio and conservative news programs.
Even in the bitter immigration debates of the past decade, children who were illegally brought to the United States at young ages by their parents, and who graduated from high school or sought to enter the military, have held a sympathetic place in the conversation.
They were branded as Dreamers for their inspiring personal stories and regarded by members of both parties as deserving of a special status. Opinion polls have found the public overwhelmingly supports granting them some form of legal standing that allows them to stay and work in the country where they were raised.
Mr. Trump, who made his hard-line immigration stance a calling card of his presidential campaign, savaged Mr. Obama for taking executive action in 2012 to protect Dreamers, calling his action unconstitutional and illegal, and vowing to immediately terminate the program if he won the White House.
But Mr. Obama made a personal appeal to his successor about the program and said it was one of the few initiatives he would speak out to defend after leaving office. And after being sworn in, Mr. Trump began to equivocate, musing aloud about the fate of “these incredible kids,” and promising to deal with them with “great heart” even as his core supporters complained that he was betraying an important campaign promise.
In recent weeks, his dilemma has grown more dramatic, after 10 state attorneys general wrote to Mr. Sessions, threatening to mount a legal challenge to DACA unless the administration phased out the program by Sept. 5. In a recent meeting at the White House, Mr. Sessions informed Mr. Trump he would not defend what he considered an unconstitutional order in court, according to people familiar with the conversation, and numerous officials at the White House and the Department of Homeland Security made the case to the president that his administration would look foolish if it argued in favor of preserving it.
In June, the administration ended a similar program Mr. Obama created in 2014 to expand eligibility for DACA and give legal status to as many as five million parents of citizens and legal permanent residents. That order was blocked by a legal challenge by the State of Texas, and the Supreme Court announced last year that it had deadlocked on the case, 4 to 4.
The attorneys general said if Mr. Trump did not take similar action to terminate DACA, they would amend the Texas lawsuit to include it and work to have a court overturn the program along with the other two.
As rumors about Mr. Trump’s impending move to end DACA ran rampant in recent days, advocacy groups and progressive activists agitated strongly against the decision, warning that it would be particularly divisive in the wake of the racially charged violence in Charlottesville, Va., last month.