The House committees conducting the impeachment inquiry have sent a letter to acting White House Chief of Staff Mick Mulvaney to seek his testimony about the Trump administration’s holding up millions in military aid to Ukraine.

The chairman of the three House panels said the investigation “has revealed that you may have been directly involved in an effort orchestrated” by the president and his personal lawyer Rudy Giuliani paused the nearly $400 million in aid to pressure Ukrainian President Volodymyr Zelensky to investigate Joe Biden.

They write that the new probes “would benefit President Trump’s personal political interests, and jeopardized our national security in attempting to do so.”

Mulvaney has been asked to appear Friday before the committees.

The three lawmakers — Rep. Adam Schiff of Intelligence, Rep. Eliot Engel of Foreign Affairs and Rep. Carolyn Maloney, the acting chairwoman of the Oversight — also warned Mulvaney that being a no-show could have significant consequences.

“Your failure or refusal to appear at the deposition, including at the direction or behest of the President, shall constitute further evidence of obstruction,” the three Democrats wrote.

They noted that during a White House news conference last month, Mulvaney admitted Trump asked for the funds to be held up. Asked why the president paused the aid, Mulvaney responded: “Did he also mention to me in the past the corruption related to the DNC server? Absolutely. No question about that. But that’s it, and that’s why we held up the money,” Mulvaney told reporters.

He later walked back those remarks.