WASHINGTON – The Trump administration on Tuesday started winding down an Obama-era immigration program designed to protect undocumented immigrants who were brought into the United States as children, but invited Congress to preserve it through legislation within six months.

Attorney General Jeff Sessions called the protections provided by the Deferred Action for Childhood Arrivals (DACA) program an "unconstitutional exercise of authority by the executive branch."

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The Department of Homeland Security will immediately stop accepting applications to the DACA program – but current recipients would not be affected until March 5 of next year. This gives Congress time to find a legislative solution to replace the program, which currently shields some 800,000 young immigrants from deportation.

Announcing the U.S. would rescinding the Obama administration's 2012 order that created the program, Sessions said the effect of providing "amnesty" for young undocumented immigrants meant "aliens" took jobs of Americans. It also contributed to a surge of unaccompanied minors on the southern border that yielded terrible humanitarian consequences, he added.

"We cannot admit everyone who would like to come here," Sessions said. "It's just that simple."

President Trump himself has yet to fully comment on the changes to the program, other than an early Tuesday tweet. "Congress, get ready to do your job - DACA!" Trump said ahead of the announcement.

According to a statement from the department of Homeland Security, immigrants with DACA permits that expire before March 5 can apply for a two-year renewal, but must do so before Oct. 5.

And even if Congress does not take action by next March, officials said there is no guarantee that DACA members will be deported – the priority will continued to be on undocumented migrants who have committed crimes.

"We are people of compassion and we are people of law," Sessions said. "There is nothing compassionate about not enforcing immigration laws."

Signaling his opposition to the DACA program on Tuesday, Trump retweeted comments from an account called "the Trump Train," including one that said "we are a nation of laws. No longer will we incentivize illegal immigration."

The announcement quickly drew scorn from Democratic lawmakers who accused Trump of seeking to get rid of hundreds of thousands of migrants who contribute to the U.S. economy.

Supporters of the program also said there is little chance that Congress, already divided over issues like health care and tax changes, will vote to resurrect a much-disputed immigration program.

Even some Republicans had also asked Trump to hold off on rescinding DACA, arguing against adding a major immigration item to an already crowded legislative agenda.

American business leaders also objected to Trump's immigration moves. Tim Cook, the CEO of Apple, tweeted that "250 of my Apple coworkers are #Dreamers. I stand with them. They deserve our respect as equals and a solution rooted in American values."

One way or another, courts are also expected to be involved in resolving the dispute over DACA.

A group of Republican attorneys general from 10 states have threatened to file a lawsuit against the DACA program if Trump doesn't act to end it.

Attorneys for undocumented immigrants involved in the program have also threatened lawsuits if it it is ended.

The American Civil Liberties Union, which has also pledged to defend DACA in court, told Trump in a tweet Tuesday that "you are manufacturing a crisis."

"You must keep #DACA in place until Congress passes a stand alone Dream Act," the group said.

Sen. Lindsey Graham, R-S.C., described Obama's original order as an overreach, but also said Congress needs to address the issue because so many people are affected.

"I equally understand the plight of the Dream Act kids who – for all practical purposes – know no country other than America," Graham said. "If President Trump makes this decision we will work to find a legislative solution to their dilemma.”

Democrats, meanwhile, strongly opposed ending the program.

"President Trump is mistaken if he believes splitting up families and deporting people who were brought here as small children and have known no other home comports with American values or will make our country greater," said Rep. Steny Hoyer, D-Md., the House Democratic whip.