President Trump, speaking at the White House on Thursday, announced that he would "immediately" issue an executive order to get an accurate count of non-citizens and citizens in the United States -- a measure Trump said would be "far more accurate" than relying on a citizenship question in the 2020 census.

The move would make use of "vast" federal databases and free up information sharing among all federal agencies concerning who they know is living in the country, Trump said.

"Today I'm here to say we are not backing down in our effort to determine the citizenship status of the United States population," the president told reporters in the Rose Garden, after slamming "far-left Democrats" seeking to "conceal the number of illegal aliens in our midst."

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"We will leave no stone unturned," Trump asserted. He called legal opposition to adding a citizenship question to the 2020 census "meritless," but said the ongoing judicial morass in several federal district courts made it logistically impossible to resolve the matter before the 2020 census forms needed to be printed.

Speaking after Trump, Attorney General Bill Barr said the information collected via the executive order could be useful in determining the makeup of the Electoral College and congressional apportionment.

"That information will be used for countless purposes. For example, there is a current dispute over whether illegal aliens can be included for apportionment purposes. ... We will be studying this issue," Barr said.

Census counts -- which by law include illegal immigrants -- have been used to determine the allocation of seats in the House of Representatives for the next 10 years, the number of electors afforded each state in the Electoral College and the distribution of some $675 billion in federal spending.

The Census Bureau's own experts have said requiring information about citizenship would discourage illegal immigrants from participating and lead to a less accurate count. That, in turn, would redistribute money and political power away from many cities led by Democrats where immigrants tend to cluster.

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Barr also agreed with Trump that the Supreme Court decision last month posed insurmountable "logistical" -- but not "legal" -- barriers to asking the citizenship question on the census. The government already has started the lengthy and expensive process of printing the census questionnaire without the question.

Additionally, Barr slammed media reports that the White House would issue an executive order in an attempt to illegally force a citizenship question on the census. "In the hysterical mode of the day," Barr said, media outlets speculated that Trump simply would add the question to the census unilaterally.

"This has never been under consideration," Barr said.

Many Democrats promptly characterized the president's move as a "retreat," and condemned the news conference. Others vowed to consider challenging the executive order in court.

"President Trump is so intent on intimidating communities of color that even when the courts and rule of law thwart him, he still tries to persist in his ham-handed ways," Senate Minority Leader Chuck Schumer, D-N.Y., said in a statement. "The president’s retreat on adding the misguided citizen question to the census was long overdue and is a significant victory for democracy and fair representation. Every person must be counted and no one should be intimidated by the president and his capricious behavior."

Reacting to the news that the Trump administration would not ask the citizenship question on the census, Elizabeth Warren quipped at a town hall, "Wow, he’s going to follow the law?"

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Trump had emphasized his exasperation at the situation earlier in the day at a White House conference focused on social media censorship of conservatives.

"We spend $20 billion on a census," Trump told attendees. "They go through houses, they go up, they ring doorbells, they talk to people. How many toilets do they have? How many desks do they have? How many beds? What's their roof made of? The only thing we can't ask is, are you a citizen of the United States. Isn't it the craziest thing?"

DOJ spokesperson Kerri Kupec told Fox News that Trump's "alternative path" ended the legal fight over the citizenship question.

"The Supreme Court held that Secretary Ross reasonably concluded that including the citizenship question on the 2020 decennial census would provide the most complete and accurate citizenship information, but it invalidated his decision to include that question on other grounds," Kupec said.

She added: "The Department of Justice disagrees with the Supreme Court’s decision. Today’s Executive Order represents an alternative path to collecting the best citizenship data now available, which is vital for informed policymaking and numerous other reasons. Accordingly, the Department will promptly inform the courts that the Government will not include a citizenship question on the 2020 decennial census."

Kristen Clarke, the executive director and president of the Lawyers’ Committee for Civil Rights Under Law, which has challenged the citizenship question in court, told Fox News she had "grave concerns about the administration’s continued dogged pursuit of citizenship information for what appear to be improper, discriminatory and unconstitutional uses."

"There simply was no legally sound basis that would have allowed President Trump to make an end run around the Supreme Court’s decision blocking the citizenship question on the Census," Clarke said. "By prolonging this battle, the administration has sowed chaos and confusion. ... We will use every tool in our arsenal to police the administration should their executive action violate constitutional or legally-protected rights."

The president had said last week that he was "very seriously" considering an executive order to try to force the citizenship question's inclusion.

Earlier Thursday, ABC News first reported that Trump would "back down" from his efforts to add a citizenship question to the 2020 census, and instead would "take executive action that instructs the Commerce Department to obtain an estimate of U.S. citizenship through other means."

Multiple sources confirmed that reporting to Fox News.

Trump's administration has faced numerous roadblocks to adding the question, beginning with the ruling by the Supreme Court temporarily barring its inclusion on the grounds that the government's justification was insufficient. The court challenged the reasoning given that the Justice Department wanted the question to better enforce the Voting Rights Act.

Chief Justice John Roberts joined the Supreme Court's four more liberal members in last month's decision and was openly skeptical about that justification.

A federal judge on Wednesday also rejected the Justice Department's plan to replace the legal team fighting for inclusion, a day after another federal judge in Manhattan issued a similar ruling, saying the government can't replace nine lawyers so late in the dispute without satisfactorily explaining why.

The Trump administration had given conflicting signals on the subject -- initially planning to print the census forms without the citizenship question and then renewing the push to include it.

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Trump has offered several explanations for why he believed the question was necessary to include in the once-a-decade population count.

"You need it for Congress, for districting. You need it for appropriations. Where are the funds going? How many people are there? Are they citizens? Are they not citizens? You need it for many reasons," he told reporters last week.

Fox News' Bill Mears, John Roberts, Mike Emanuel, Ronn Blitzer and The Associated Press contributed to this report.