Secretary of State Mike Pompeo accused lawmakers of “intimidating and bullying” five current and former officials into providing documents and testimony in the impeachment inquiry against President Donald Trump.

“I’m concerned with aspects of the Committee’s request that can be understood only as an attempt to intimidate, bully & treat improperly the distinguished professionals of the Department of State, including several career FSOs [Foreign Service Officers],” Pompeo tweeted.

“Let me be clear: I will not tolerate such tactics, and 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,” he added.

Pompeo wrote Tuesday to the chairman of the House Foreign Affairs Committee, Eliot Engel (D-New York), saying that the proposed dates for depositions “do not provide adequate time for the Department and its employees to prepare” and that the request was “not feasible.”

Engel and the chairmen of the House Intelligence and Oversight committees, Adam Schiff (D-California) and Elijah Cummings (D-Maryland) responded that any effort to prevent those officials from speaking to Congress “is illegal and will constitute evidence of obstruction of the impeachment inquiry.”

Pompeo confirmed Wednesday morning that he was on the July 25 phone call between Trump and the president of Ukraine, during which Trump requested Ukraine to investigate political opponent Joe Biden.

In a released, non-verbatim transcript of the phone call, Trump hinted that Biden had cause Ukraine’s top prosecutor to be fired, because he had been investigating tax evasion charges against a gas company that Biden’s son worked for.

“There’s a lot of talk about Biden’s son, that Biden stopped the prosecution, and a lot of people want to find out about that so whatever you can do with the Attorney General would be great,” Trump told the Ukrainian president. “Biden went around bragging that he stopped the prosecution so if you can look into it… It sounds horrible to me.”

There is no evidence of wrongdoing by Biden or his son.

The three chairmen wrote to Deputy Secretary of State John Sullivan Tuesday night that Pompeo being on the phone call means he has “an obvious conflict of interest.”

“Secretary Pompeo is now a fact witness in the House impeachment inquiry,” the three men wrote. “He should immediately cease intimidating Department witnesses in order to protect himself and the President.”

Pompeo was subpoenaed by the congressional committees last Friday for failing to produce documents “related to reported efforts by President Trump and his associates to improperly pressure the Ukrainian government to assist the President’s bid for reelection.”

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He has until Oct. 4 to provide the documents.