 -- The Trump administration is rescinding the Deferred Action for Childhood Arrivals (DACA) program and will phase it out over the next six months, leaving the fates of Dreamers in the hands of Congress.

"To have a lawful system of immigration that serves the national interest. We cannot admit everyone who would like to come here. It's just that simple," Attorney General Jeff Sessions said at the Department of Justice, announcing the administration's decision Tuesday. He did not take any questions.

The Justice Department recommended to the Department of Homeland Security and the White House that the DHS should begin "an orderly lawful wind down, including the cancellation of the memo that authorized this program," according to Sessions.

"This administration's decision to terminate DACA was not taken lightly. The Department of Justice has carefully evaluated the program's constitutionality and determined it conflicts with our existing immigration laws," Elaine Duke, the acting homeland security secretary, said in a press release.

Since the program's initiation in 2012 by the Obama administration, nearly 800,000 unauthorized immigrants who came to the United States as children have been granted protection from deportation under DACA.

As ABC News earlier reported, the new policy will stop accepting new applications for legal status dated after Sept. 5.

"I want to be clear that no new initial requests or associated applications filed after today will be acted on," Duke said.

Some details of the new policy, according to the two administration officials:

The administration won't consider new applications for legal status dated after Sept. 5.

People not already protected by the program are out of luck, although pending applications filed before Tuesday will continue to be processed.

Anyone with a DACA permit expiring between now and March 5, 2018, may apply for a two-year renewal of protected status. Those applications must be submitted by Oct. 5.

Other Dreamers' protected status will end as early as March 6, 2018.

After Sessions' announcement, President Donald Trump said in a statement that he looks forward to working with Republicans and Democrats to "resolve the DACA issue with heart and compassion — but through the lawful democratic process."

He also reiterated that his administration would prioritize deporting criminals rather than Dreamers.

"Our enforcement priorities remain unchanged. We are focused on criminals, security threats, recent border-crossers, visa overstays, and repeat violators," Trump said. "I have advised the Department of Homeland Security that DACA recipients are not enforcement priorities unless they are criminals, are involved in criminal activity, or are members of a gang."

After making comments on tax reform at the White House Tuesday afternoon, Trump addressed those covered by the policy and defended the decision by pointing out that those who benefited are now older than they were when they arrived in the country.

"People think in terms of children, but they're really young adults," said Trump. "I have a love for these people, and hopefully now Congress will be able to help them and do it properly."

In his announcement, Sessions emphasized the importance of "enforcing the law."

"We are people of compassion, and we are people of law, but there is nothing compassionate about the failure to enforce immigration laws," he said. "Enforcing the law saves lives, protects communities and taxpayers and prevents human suffering."

"The compassionate thing to do is end the lawlessness, enforce our laws and, if Congress chooses to make changes to those laws, to do so through the process set forth by our founders, in a way that advances the interests of the American people," he added.

The administration made its announcement on DACA on Sept. 5 in response to a deadline set by Texas Attorney General Ken Paxton and nine other state attorneys general, who said they planned to expand a lawsuit against Deferred Action for Parents of Americans (DAPA) — an Obama-era policy that Texas and 25 other states fought and courts blocked before the Trump administration reversed it in June — to include a challenge to the DACA program if it was not ended.

"Our collective wisdom is that the policy is vulnerable to the same legal and constitutional challenges" as the DAPA program, Sessions said.

President Barack Obama implemented DACA on June 15, 2012, intending for the program to be temporary and for Congress to pass a more comprehensive immigration reform bill.

Sessions today called the DACA program an "unconstitutional exercise of authority by the executive branch" and said it showed "disrespect for the legislative process."

Before the announcement, Trump hinted on Twitter that he would ultimately leave it up to Congress what to do about the Dreamers.

"Congress now has the opportunity to advance responsible immigration reform that puts American jobs and American security first," Trump said in his statement today, going on to tout the Raise Act, introduced by Sens. Tom Cotton, R-Ark., and David Perdue, R-Ga., which would change the immigration system to prioritize high-skilled English-speaking immigrants.

Asked at Tuesday's White House press briefing why Sessions was the person to make the announcement rather than the president himself, press secretary Sarah Sanders characterized the plan as a "legal decision" that would fall to the attorney general.

"It would be the Department of Justice to make a legal recommendation and that's what they did," said Sanders, later adding, "This was a legal issue because there was a court decision that had to be made."

Sanders further addressed the possibility of Congress being unable to reach a permanent solution on the matter by March 5, the end date set by the administration's phase-out plan, saying, "If Congress doesn't want to do the job that they were elected to do, then maybe they should get out of the way and let someone else do it."

Congress has been struggling for years to pass legislation that would overhaul the country's immigration system, with the most recent attempt in 2013. That immigration bill — drafted by eight Republican and Democratic senators, known as the Gang of Eight — which would have given millions of unauthorized immigrants a path to citizenship, passed the Senate but failed in the House.

ABC News' Jonathan Karl and John Santucci contributed to this report.