Mick Mulvaney
© AP/Evan Vucci
Acting WH Chief of Staff Mick Mulvaney
Acting White House Chief of Staff Mick Mulvaney will defy a subpoena seeking his testimony before the House Intelligence Committee as part of the House Democrats' impeachment investigation into President Donald Trump, according to Fox News.

Mulvaney was scheduled to testify Friday in the impeachment inquiry — but like several other administration officials, he was not expected to appear.

The White House said Mulvaney won't participate in what it called a "ridiculous, partisan, illegitimate proceeding." The House issued a subpoena for Mulvaney on Thursday, but he's still unlikely to appear, White House Counselor Kellyanne Conway said.

State Department official Catherine Croft testified last week that Mulvaney had put a hold on nearly $400 million in military aid to Ukraine four months agobefore President Trump's phone call with Ukrainian President Volodymyr Zelensky that spawned a whistle-blower report, and the impeachment investigation.

During the call, President Trump pressed Zelensky to investigate Democrat presidential candidate Joe Biden and his son, Hunter. Investigators are trying to determine whether the Congress-approved military aid was tied to the president's request for a personal political favor.

President Trump and Zelensky have denied any pressure was applied to investigate the Biden family and the White House, in a nod to transparency, released a transcript of the world leaders' call as evidence that no wrongdoing occurred.

"There was no blackmail," Zelensky told reporters in October. "We are not servants. We are an independent country."

Mulvaney's decision not to testify comes after House Democrats released the closed-door depositions of George Kent, the deputy assistant secretary of state for European and Eurasian Affairs, and William Taylor, the U.S. Ambassador to Ukraine. Both officials are slated to publicly testify before congressional investigators next week.