(CNN) The Trump administration on Tuesday formally announced the end of DACA -- a program that had protected nearly 800,000 young undocumented immigrants brought to the US as children from deportation.

The Department of Homeland Security will stop processing any new applications for the program as of Tuesday and rescinded the Obama administration policy, Deferred Action for Childhood Arrivals.

"I am here today to announce that the program known as DACA that was effectuated under the Obama administration is being rescinded," Attorney General Jeff Sessions said Tuesday at the Justice Department.

In the five years since DACA was enacted, the nearly 800,000 individuals who have received the protections have started families, pursued careers and studied in schools and universities across the United States. The business and education communities at large have joined Democrats and many moderate Republicans in supporting the program, citing the contributions to society from the population and the sympathetic fact that many Dreamers have never known another home than the US.

In a statement after his agencies and attorney general announced the decision, President Donald Trump blamed former President Barack Obama for creating the program through executive authority and urged Congress to come up with a solution.

"It is now time for Congress to act!" he said.

Trump said that winding down the program would be more considerate than letting the courts end it but emphasized he stands by his "America First" agenda.

"As I've said before, we will resolve the DACA issue with heart and compassion -- but through the lawful Democratic process -- while at the same time ensuring that any immigration reform we adopt provides enduring benefits for the American citizens we were elected to serve," Trump said. "We must also have heart and compassion for unemployed, struggling and forgotten Americans."

Later, Trump told reporters he feels compassion for those affected, but "long term it's going to be the right solution."

"I have a great heart for these folks we're talking about. A great love for them and people think in terms of children but they're really young adults. I have a love for these people and hopefully now Congress will be able to help them and do it properly," he said ahead of a meeting on tax reform.

The administration also announced a plan to continue renewing permits for anyone whose status expires in the next six months, giving Congress time to act before any currently protected individuals lose their ability to work, study and live without fear in the US.

The Trump administration pitched the move as the "least disruptive" option available after facing a threat from 10 conservative state attorneys general to challenge the program in court, according to senior administration officials briefing reporters on the move during a conference call conducted on condition of anonymity.

Sessions had determined that the program would not be likely to withstand that court challenge, he said.

"The Department of Justice cannot defend this overreach," Sessions said. "There is nothing compassionate about the failure to enforce immigration laws. Enforcing the law saves lives, protects communities and taxpayers, and prevents human suffering. Failure to enforce the laws in the past has put our nation at risk of crime, violence and even terrorism. The compassionate thing is to end the lawlessness, (and) enforce our laws."

But in an internal email sent to all DHS staff, acting Homeland Security Secretary Elaine Duke struck a softer tone than the official line, while still criticizing the previous administration.

"I am very aware of the consequences of this action, and I sympathize with the DACA recipients whose futures may now be less certain," Duke said in the memo, obtained by CNN. "But I am also frustrated on their behalf. DACA was never more than parole -- a bureaucratic delay -- that never promised the rights of citizenship or legal status in this country. And for that reason, DACA was fundamentally a lie that left recipients in two-year cycles of uncertainty."

DHS spokesman David Lapan confirmed the authenticity of the memo that CNN obtained.

Congress faces deadline

The move sets a clock for Congress to act to preserve the program's protections before the DACA recipients begin losing their status March 5, 2018.

In a statement, House Speaker Paul Ryan reiterated his aspiration that Congress will reach a solution in time.

"It is my hope that the House and Senate, with the president's leadership, will be able to find consensus on a permanent legislative solution that includes ensuring that those who have done nothing wrong can still contribute as a valued part of this great country," Ryan said.

Senate Majority Leader Mitch McConnell praised Trump's move

"President Obama wrongly believed he had the authority to re-write our immigration law. Today's action by President Trump corrects that fundamental mistake," McConnell said in a statement. "This Congress will continue working on securing our border and ensuring a lawful system of immigration that works."

No one's DACA status will be revoked before it expires, administration officials said, and any applications already received by Tuesday will be processed.

Anyone who's status expires by March 5 has one month to apply for a new two-year permit, and those applications will be processed.

If Congress were not to act, and DACA begins to expire, nearly 300,000 people could begin to lose their status in 2018, and more than 320,000 would lose their status from January to August 2019. More than 200,000 recipients have their DACA expiring in the window that DHS will allow renewal.

Deportations?

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Speaking with reporters on a conference call on condition of anonymity, DHS did not rule out that anyone with expired DACA would then be subject to deportation. Immigration and Customs Enforcement said it will continue to prioritize for enforcement people with criminal records, people who re-enter the US illegally and those with final orders of removal.

But officials said there will be no formal guidance that former DACA recipients are not eligible for deportation, and ICE officers in the field who encounter them will be making a case-by-case judgment as to whether to arrest that individual and process them for deportation.

The administration insisted its approach was designed to offer some security to DACA recipients, emphasizing that if it had allowed the courts to decide the issue, then would have been risking an immediate and abrupt end to DACA at the hands of a judge.

But it also was made clear that once DACA begins to expire, if Congress doesn't act, then people formerly protected "would be like any other person who's in the country illegally," according to a senior DHS official.

All of the information provided to the government by DACA applicants will remain in the DHS system. US Citizenship and Immigration Services, which administers the program, will give that information to ICE if requested if "there's a significant law enforcement or national security interest," an official said.

While they won't be specifically targeted, DHS said, they could be arrested and deported if they are encountered by ICE officers. And their information, which they provided extensively for their DACA applications, will continue to reside in DHS systems and could be accessed if officers feel it's necessary in the course of an investigation.

DHS said it had on plans to issue formal guidelines on how former DACA recipients -- or their information -- will be treated beyond the current operating procedures of DHS.

"To be clear, what ICE is doing now is what Congress intended, we're actually enforcing the law the way it is written," said a senior ICE official. "(This is t)he first President who's asked us to enforce the law the way it is written and not asked us to have some executive interpretation of the law."

The officials placed the onus on Congress to make any changes to the system.

Obama speaks out

The former president issued a rare statement criticizing the move by his successor to rescind one of his signature programs, calling it "basic decency."

He also pushed back on the administration's claims that its hands were tied legally.

"Let's be clear: The action taken today isn't required legally," Obama said. "It's a political decision, and a moral question. 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."

Obama then extolled the virtues of DACA recipients while implicitly rebutting the administration's arguments for ending the program.

"They are that pitcher on our kid's softball team, that first responder who helps out his community after a disaster, that cadet in ROTC who wants nothing more than to wear the uniform of the country that gave him a chance," Obama said. "Kicking them out won't lower the unemployment rate, or lighten anyone's taxes, or raise anybody's wages ... Ultimately, this is about basic decency."