The Trump administration is moving to end a program that protected 800,000 young, undocumented immigrants in the United States.

Many of the immigrants were children when they entered the country illegally with their parents.

President Donald Trump approved the move, but it was Attorney General Jeff Sessions who announced the change in policy.

"We cannot admit everyone who wants to come here," Sessions told reporters on Tuesday. "All cannot be accepted."

He added that limiting immigration "means we are properly enforcing our laws."

The administration is ending a five-year-old program that former President Barack Obama created through an executive order. The program was known as Deferred Action for Childhood Arrivals (DACA), but the young immigrants also became known as "Dreamers."

DACA gave the immigrants legal permission to work, study and serve in the U.S. military. It also prevented them from being sent back to their home country.

In a statement, the president said he does not believe it is right to punish the young people for the actions of their parents. But he added, "As I've said before, we will resolve the DACA issue with heart and compassion – but through the lawful democratic process."

Trump accused Obama of going around Congress to put the program in place through executive order. He noted that DACA faces legal tests in several states. He said the Justice Department had advised him the program was "unlawful and unconstitutional" and not likely to be successfully defended in court.

All new DACA applications will be stopped. But officials said people currently in the program will not be affected until March 5, 2018. Existing permits that end before that date can be extended and will be honored for up to two years.

Trump said the extended "wind-down" now puts the program's future in the hands of Congress. "I am not going to just cut DACA off, but rather provide a window of opportunity for Congress to finally act," his statement said.

Several Congressional Republicans had urged the president not to cancel DACA. Paul Ryan, the Speaker in the Republican-controlled House of Representatives, released a statement on Tuesday. It urged lawmakers to work for a solution for the "young people who came to this country through no fault of their own."

Ryan said he hoped the House and Senate can find a permanent legislative fix to the problem. He also called for new legislative discussions on border security and other immigration issues.

Former President Obama criticized the decision as "cruel" and "self-defeating." Obama defended his approval of the program, noting he waited years for Congress to act on immigration reforms, but they did not.

Responding in a statement on Facebook, Obama said he believes the Trump administration decision was political, and not made for legal reasons.

"Whatever concerns or complaints Americans may have about immigration in general, we shouldn't threaten the future of this group of young people who are here through no fault of their own, who pose no threat, who are not taking away anything from the rest of us," the statement said.

Demonstrators marched in several U.S. cities to protest the decision. In Denver, Colorado, hundreds of teachers and students gathered outside Metro State University. Some carried signs reading, "No borders, no nations, no racists, no deportations."

Protests were also held near the White House, outside Trump Tower in New York City and in downtown Los Angeles.

I'm Bryan Lynn.

Bryan Lynn wrote this story for Learning English. His story was based on reports from VOANews, the Associated Press and Reuters. George Grow was the editor.