The Democratic-led U.S. House Judiciary Committee asked a federal court on Wednesday to compel former White House Counsel Don McGahn to testify about President Donald Trump's alleged efforts to impede the federal probe into Russian meddling in the 2016 election.

In a lawsuit filed in U.S. District Court in Washington, the committee insisted that McGahn's testimony is needed to decide whether to recommend the impeachment of the Republican president over actions that Democrats view as criminal attempts to obstruct then-Special Counsel Robert Mueller's 22-month investigation.

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"McGahn ... is the most important witness, other than the president, to the key events that are the focus of the Judiciary Committee's investigation," the lawsuit said.

The move represented the latest step toward impeachment by Democrats in the House of Representatives, who last week cited their impeachment drive in a court petition seeking access to Mueller's grand jury evidence.

Democrats predicted that the lawsuit, if successful, would dismantle a White House strategy to stonewall congressional probes by directing current and former Trump aides, including McGahn, not to testify or provide documents to investigators.

But the litigation could take months to resolve, with the lawsuit being filed as the political focus of many House lawmakers pivots toward the 2020 elections. The committee urged quick action by the court, saying that its inquiries will end with the current Congress.

Republicans criticized the lawsuit as a theatrical gesture geared more toward voters than congressional oversight.

"Their insistence on having Don McGahn testify publicly before the cameras further proves they are only interested in the fight and public spectacle of an investigation, but not actually in obtaining any real information," Representative Doug Collins, the panel's top Republican said in a statement.

McGahn emerged as the star witness in the 448-page Mueller report released in April, but he defied a committee subpoena to testify a month later after the White House directed him not to cooperate with the panel.

McGahn told Mueller's investigation team that Trump pressed him repeatedly to have the special counsel removed and then to deny that he had been instructed to do so.

The lawsuit said Trump has denounced the Mueller probe as a "witch hunt" or a "hoax" over 300 times and noted that the president has also repeatedly disputed McGahn's claim about being directed to seek Mueller's removal.

"The fact that the president is trying to block him while simultaneously disputing what he said ... makes it that much clearer that there's no basis to block his testimony," one Democratic committee lawyer said.

Democrats said McGahn could also testify about alleged efforts by Trump to pressure then-Attorney General Jeff Sessions to redirect the Russia probe away from his 2016 campaign, as well as White House discussions surrounding the firing of FBI Director James Comey.

"The Judiciary Committee is now determining whether to recommend articles of impeachment," the lawsuit said.

"But it cannot fulfill this most solemn constitutional responsibility without hearing testimony from a crucial witness to these events: former White House Counsel Donald F. McGahn II."

Articles of impeachment represent a formal accusation of misconduct that would require 218 votes to pass the 435-member House. If the House approved an impeachment resolution against Trump, it would be up to the Republican-controlled Senate to hold a trial and possibly remove him from office.

Democrats said McGahn could deliver devastating testimony against Trump, similar to the testimony against former President Richard Nixon by then-White House Counsel John Dean during the Watergate era.

"Don McGahn is Donald Trump's John Dean," a second Democratic lawyer for the committee said.

Mueller's investigation found numerous contacts between Moscow and the Trump campaign but did not establish enough evidence to prove that a conspiracy occurred.

On obstruction, Mueller did not determine whether Trump committed a crime but also did not exonerate the president. Russia has denied meddling in the election.

(Cover: Then White House counsel Donald McGahn at a Senate Judiciary Committee hearing on Capital Hill, September 27, 2018. /VCG Photo)