Secretary of State Mike Pompeo on Tuesday pushed back on House Democrats' attempt to depose State Department officials as part of the ongoing impeachment inquiry into President Donald Trump.

Pompeo said in a tweet that he is "concerned with aspects" of House committee leaders' requests "that can be understood only as an attempt to intimidate, bully, & treat improperly the distinguished professionals of the Department of State."

"Let me be clear: I will not tolerate such tactics," Pompeo said in a letter to House Foreign Affairs Committee Chairman Eliot Engel, D-N.Y., which he shared as part of that tweet.

"I will use all means at my disposal to prevent and expose any attempts to intimidate the dedicated professionals whom I am proud to lead and serve alongside at the Department of State," Pompeo wrote.

Pompeo TWEET

Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky was flagged in an explosive whistleblower complaint that was made public last week, along with a five-page memorandum of the call itself. The complaint accuses Trump of "using the power of his office to solicit interference from a foreign country in the 2020 U.S. election" when he asked Zelensky to investigate unsubstantiated allegations of wrongdoing against former Vice President Joe Biden and his son Hunter.

The Wall Street Journal first reported Monday evening that Pompeo was on that phone call between the two world leaders. Pompeo had not previously acknowledged having any involvement in the call. NBC News confirmed the Journal's report. Pompeo himself said during a Wednesday morning press conference in Italy that he was on the call.

On Friday, leaders from three Democrat-led House committees subpoenaed Pompeo for documents related to the impeachment inquiry into Trump, which was formally announced by House Speaker Nancy Pelosi, D-Calif., earlier in the week.

The panels also told Pompeo that they had scheduled depositions over the next two weeks with five State Department officials. Pompeo said this timeline is "not feasible" in his letter.