House Foreign Affairs Committee Chairman Eliot Engel, D-N.Y., announced Tuesday that he supports opening a formal impeachment inquiry into President Trump, lending high-powered support for the prospective proceedings that now have the support of nearly half of the Democratic caucus.

Still, Engel's announcement puts him at odds with other House leaders, including Speaker Nancy Pelosi, and comes as the longtime New York representative faces a primary challenge from the party's liberal wing backed by Justice Democrats -- the group that helped Alexandria Ocasio-Cortez dethrone incumbent Joe Crowley in 2018.

"The American people want, and deserve, the truth," Engel wrote on Twitter. "I believe the House must pursue a formal impeachment inquiry."

In an attached statement, Engel said the president has "abused the power of his office in an effort to stymie a legitimate investigation into his campaign's involvement with Russia."

Engel also implied, contrary to former Special Counsel Robert Mueller's testimony, that Trump would have faced prosecution for obstruction of justice, if not for "Justice Department guidance that a sitting president can't be indicted." During his testimony last week, Mueller clarified that his office made no determination as to whether Trump had committed a crime.

At least 112 other U.S. House members --- 111 Democrats, and independent Justin Amash -- have come out in support of an impeachment inquiry, including 16 members of the House Judiciary Committee that would oversee the proceedings. There are 235 Democrats in the House.

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A total of 18 members have backed an impeachment inquiry since Mueller's testimony put public attention back on the report last week, even as the former FBI director's halting performance disappointed top Democrats.

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Engel was one of more than two dozen Democrats who voted to keep an impeachment push against Trump by Rep. Al Green, D-Texas, alive earlier this month, after Trump's incendiary comments directed at four progressive women lawmakers caused an outcry on Capitol Hill. At the time, Engel said he wanted to keep the possibility of impeachment alive, but did not support a formal inquiry.

House Foreign Affairs Chairman Rep. Eliot Engel, D-NY, announced his support for a formal impeachment inquiry. (AP Photo/Jacquelyn Martin)

In lieu of a formal impeachment inquiry, Judiciary Committee Democrats said Friday that they are proceeding with what they called an “impeachment investigation,” insisting that Mueller delivered damning testimony against Trump despite concerns from many on the left that his appearance broke little new ground.

Judiciary Committee Chairman Jerrold Nadler, D-N.Y., and the committee filed a petition in D.C. federal court to obtain grand jury materials from the Mueller investigation. The petition claimed the panel needs the information in order to determine whether to recommend articles of impeachment.

"To meaningfully consider whether to exercise this authority -- as well as to exercise its other pressing legislative and oversight responsibilities -- the Committee must obtain evidence and testimony in a timely manner," the filing reads.

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Nadler called the grand jury materials “critically important” for their investigation. In the petition, Democrats on the committee noted that because Justice Department policies do not allow the prosecution of a sitting president, the House of Representatives is “the only institution of the federal government” that can hold Trump accountable.

“The House must have access to all evidence,” Nadler said. “We are exercising our constitutional authority. We are continuing the investigation of President Trump’s malfeasances, and we will do and consider what we have to consider including whether we should recommend Articles of Impeachment to the House. We may, we may not. It remains to be seen."

It's unclear what new information might be found in the grand jury transcripts. Many of the high-profile witnesses connected to the White House, for instance, appeared for voluntary questioning before Mueller's team rather than before the grand jury.

House Judiciary Committee Ranking Member Doug Collins, R-Ga., meanwhile, blasted Nadler's move to "sue for grand jury material to which they have no right."

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"Chairman Nadler’s legal action here is sure to fail, weakening Congress’s ability to conduct oversight now and into the future. If my colleagues want grand jury information, they should propose legislation allowing Congress to access it," he said in a statement. "Democrats want to convince their base they’re still wedded to impeachment even after this week’s hearing, but a baseless legal claim is an odd way to show that.”

Fox News' Brooke Singman and The Associated Press contributed to this report.