Jake Tapper 10252019
PHOTO: CNN
Jake Tapper 10252019
Now playing
02:16
Jake Tapper: The facts are bad for the President
Connolly
PHOTO: CNN
Connolly
Now playing
03:51
'I will not be lectured' on bipartisanship: Lawmaker fires back at Jim Jordan
US President Donald Trump speaks to the press from the South Lawn of the White House after announcing and initial deal with China in Washington, DC, prior to departing to Lake Charles, Louisiana to hold a campaign rally on October 11, 2019.
PHOTO: NICHOLAS KAMM/AFP/Getty Images
US President Donald Trump speaks to the press from the South Lawn of the White House after announcing and initial deal with China in Washington, DC, prior to departing to Lake Charles, Louisiana to hold a campaign rally on October 11, 2019.
Now playing
02:28
Romney says he's 'pretty sure' Trump will win 2024 nomination if he runs
Now playing
02:04
Senate moderates create obstacle for Biden's nominee
This picture taken 26 December 2011 shows the Pentagon building in Washington, DC.  The Pentagon, which is the headquarters of the United States Department of Defense (DOD), is the world
PHOTO: Staff/AFP/Getty Images
This picture taken 26 December 2011 shows the Pentagon building in Washington, DC. The Pentagon, which is the headquarters of the United States Department of Defense (DOD), is the world's largest office building by floor area, with about 6,500,000 sq ft (600,000 m2), of which 3,700,000 sq ft (340,000 m2) are used as offices. Approximately 23,000 military and civilian employees and about 3,000 non-defense support personnel work in the Pentagon. (Photo credit should read STAFF/AFP via Getty Images)
Now playing
04:30
Pentagon report gives insight on White supremacists in active military
Now playing
03:57
GOP senator continues to push riot conspiracy theory
Now playing
02:08
Cabinet secretary explains why he took on challenging role
Rep. Debra Haaland (D-NM), President Joe Biden
PHOTO: Leigh Vogel/Pool/Getty Images
Rep. Debra Haaland (D-NM), President Joe Biden's nominee for Secretary of the Interior, testifies during her confirmation hearing before the Senate Committee on Energy and Natural Resource, at the U.S. Capitol on February 24, 2021 in Washington, DC.
Now playing
00:59
'We need to work together': Haaland responds to question on blind loyalty
Now playing
01:35
Laughter follows awkward moment between GOP leaders
PHOTO: AFP/Getty Images/CNN
Now playing
03:11
Cabrera: GOP suddenly cares about mean tweets ... just not Trump's
Now playing
03:20
Avlon on Ron Johnson: Hyperpartisan denial is a hell of a drug
WASHINGTON, DC - JANUARY 06: Pro-Trump supporters storm the U.S. Capitol following a rally with President Donald Trump on January 6, 2021 in Washington, DC. Trump supporters gathered in the nation
PHOTO: Samuel Corum/Getty Images
WASHINGTON, DC - JANUARY 06: Pro-Trump supporters storm the U.S. Capitol following a rally with President Donald Trump on January 6, 2021 in Washington, DC. Trump supporters gathered in the nation's capital today to protest the ratification of President-elect Joe Biden's Electoral College victory over President Trump in the 2020 election. (Photo by Samuel Corum/Getty Images)
Now playing
03:04
Capitol officials say riot was planned and involved white supremacists
Then-President Donald Trump addresses supporters during a Make America Great Again rally in Erie, Pennsylvania, October 20, 2020.
PHOTO: SAUL LOEB/AFP/Getty Images
Then-President Donald Trump addresses supporters during a Make America Great Again rally in Erie, Pennsylvania, October 20, 2020.
Now playing
02:44
What Trump's released tax records mean for DA's criminal case
Now playing
02:51
'This is incredible': Burnett explains Trump's reported offer to Kim Jong Un
From left, President Joe Biden, First Lady Jill Biden, Vice President Kamala Harris and her husband Doug Emhoff, bow their heads during a ceremony to honor the 500,000 Americans that died from COVID-19, at the White House, Monday, Feb. 22, 2021, in Washington. (AP Photo/Evan Vucci)
PHOTO: Evan Vucci/AP
From left, President Joe Biden, First Lady Jill Biden, Vice President Kamala Harris and her husband Doug Emhoff, bow their heads during a ceremony to honor the 500,000 Americans that died from COVID-19, at the White House, Monday, Feb. 22, 2021, in Washington. (AP Photo/Evan Vucci)
Now playing
05:45
Biden leads nation in mourning 500,000 US Covid-19 deaths
PHOTO: CNN
Now playing
01:06
Honig: Public won't see Trump's taxes unless this happens
(CNN) —  

A key witness in the impeachment inquiry has sought for a court to decide if he should testify, caught between a House subpoena and a demand from the White House to protect President Donald Trump’s immunity from testifying to Congress.

Charles Kupperman, who served until last month as deputy national security adviser at the White House, filed a lawsuit Friday asking a federal judge to rule on whether he is obliged to testify before House investigators. The case presents a new challenge to House Democrats seeking cooperation from close aides of Trump.

Kupperman, who worked closely with former national security adviser John Bolton, is scheduled to sit Monday for questioning by the three House committees handling impeachment. The lawsuit also raises questions about Bolton’s possible future testimony, as Kupperman’s lawyer Charles Cooper also represents Bolton.

“Plaintiff is faced with irreconcilable commands by the Legislative and Executive Branches of the Government and, accordingly, seeks a declaratory judgment from this Court as to whether he is lawfully obliged to comply with a subpoena issued by the House Defendants demanding his testimony ’[p]ursuant to the House of Representatives’ impeachment inquiry,’ or he is lawfully obliged to abide by the assertion of immunity from congressional process made by the President in connection with the testimony sought from Plaintiff,” the lawsuit states.

The New York Times was first to report the lawsuit.

In a statement Saturday, Cooper reiterated that the lawsuit looked to have the judiciary, not Kupperman, resolve a conflict between the President and House Democrats.

“Under our system of Government, Constitutional disputes between the Legislative and Executive Branches should be adjudicated by the Judicial Branch, not by private citizens like Dr. Kupperman,” Cooper wrote in a statement.

He added that “Dr. Kupperman takes no position on whether the command of the Legislative Branch or the command of the Executive Branch should prevail; he seeks only to carry out whichever constitutional obligation the Judicial Branch determines to be lawful and binding on him.”

Kupperman was listening in on the July 25 phone call when, according to a White House transcript, Trump pressed Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden. The lawsuit comes following three weeks of administration officials testifying in House lawmakers’ subsequent probe into the President’s dealings with Ukraine.

The lawsuit includes a copy of a letter that White House counsel Pat Cipollone sent to Cooper on Friday directing Kupperman not to comply with the subpoena and maintaining that he would be protected by “constitutional immunity.”

“The President, however, acting through the White House Counsel, has asserted that Plaintiff, as a close personal advisor to the President, is immune from Congressional process, and has instructed Plaintiff not to appear and testify in response to the House’s subpoena,” the lawsuit states.

Trump has slammed officials who have implicated him, such as the US’ top diplomat in Ukraine, Bill Taylor. Taylor testified on Tuesday that he had been told Trump would withhold military aid to Ukraine until it publicly declared investigations would be launched that could help his reelection chances — including into Biden, according to a copy of Taylor’s opening statement obtained by CNN.

But in the absence of a clear superseding power in the standoff between the White House’s professed immunity and House Democrats’ subpoena power, according to the lawsuit, Kupperman is asking the judge to decide.

“Plaintiff obviously cannot satisfy the competing demands of both the Legislative and Executive Branches, and he is aware of no controlling judicial authority definitively establishing which Branch’s command should prevail,” the challenge states.

This story has been updated.

CNN’s Evan Perez, Zachary Cohen, Manu Raju, Jeremy Herb, Lauren Fox, Kylie Atwood and Gloria Borger contributed to this report.