White House Staff Secretary Rob Porter arrives with U.S. President Donald Trump and first lady Melania Trump aboard Air Force One at Joint Base Andrews, Maryland, U.S. Feb. 5, 2018.
FILE - White House Staff Secretary Rob Porter arrives with U.S. President Donald Trump aboard Air Force One at Joint Base Andrews, Maryland, Feb. 5, 2018.

WASHINGTON - The White House has instructed two former aides to President Donald Trump not to appear at a House Judiciary Committee hearing Tuesday, saying Rick Dearborn and Rob Porter are "absolutely immune" from testifying at what the panel is calling its first impeachment hearing.

In a letter sent to the panel and obtained by The Associated Press, White House counsel Pat Cipollone wrote that the Justice Department has advised, and Trump has directed, Dearborn and Porter to defy subpoenas because of :constitutional immunity."

In a separate letter, Cipollone said that former Trump campaign manager Corey Lewandowski, who never worked for the White House, should not reveal private conversations with Trump beyond what is in special counsel Robert Mueller's report. Lewandowski is expected to attend the hearing as its sole witness on Tuesday.

FILE - White House Counsel Don McGahn sits behind U.S. President Donald Trump as the president holds a cabinet meeting at the White House in Washington, June 21, 2018.

Democrats are challenging such claims of "absolute immunity" in a lawsuit against former White House counsel Don McGahn, who defied a subpoena earlier this year on Trump's orders. They say that such a claim does not exist.

House Judiciary Committee Chairman Jerrold Nadler invited the three men to testify at the hearing as part of the panel's probe into Mueller's report and what Nadler is calling an "aggressive series of hearings" this fall to determine whether Trump should be impeached. The committee has so far been hobbled by the White House's blockade of witness testimony and document requests, and House Speaker Nancy Pelosi has said she wants to wait to see what happens in court before making a decision on impeachment.

Cipollone wrote that Dearborn and Porter were advised not to attend "because of the constitutional immunity that protects senior advisers to the president from compelled congressional testimony, and in order to protect the prerogatives of the Office of President."

In the letter regarding Lewandowski, Cipollone wrote that his conversations with Trump "are protected from disclosure by long-settled principles protecting executive branch confidentiality interests."

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