WASHINGTON, Oct. 30 (Xinhua) -- House Democrats have asked U.S. President Donald Trump's former national security advisor John Bolton to testify in their impeachment probe on Nov. 7, media outlets reported on Wednesday.
Bolton's lawyer, Charles Cooper, told NBC News that his client is "not willing to appear voluntarily."
"I stand ready at all times to accept service of a subpoena on his behalf," Cooper added.
The impeachment inquiry into Trump was initiated last month by House Speaker Nancy Pelosi after an anonymous whistleblower raised concerns about the Trump administration's interactions with Ukraine, including a July 25 phone call between Trump and his Ukrainian counterpart Volodymyr Zelensky.
Trump was alleged to have abused power by using military aid to pressure Zelensky into investigating former U.S. Vice President Joe Biden, the leading 2020 Democratic presidential candidate, so as to help his re-election campaign. The White House also allegedly tried to cover it up.
Trump has denied any wrongdoing. The White House has dismissed the allegations and made clear that it will not provide documents or witnesses to House investigators because it considered the impeachment inquiry unfair and illegitimate.
The White House's former top Europe expert, Fiona Hill, reportedly testified to impeachment investigators earlier this month that Bolton felt disturbed by the administration's efforts to get Ukraine to investigate Biden.
Hill also reportedly testified that Bolton, who left the Trump administration last month, had called Trump's personal lawyer Rudy Giuliani a "hand grenade."
Giuliani was said to have been a central figure in those alleged efforts.
House Foreign Affairs Chairman Eliot Engel, a New York Democrat, said Wednesday that the committees have not yet issued a subpoena for Bolton to testify, but if the former national security advisor does not appear voluntarily, it's "something that we would consider."
The House Rules Committee advanced a resolution Wednesday night aimed at establishing procedures for the impeachment inquiry ahead of Thursday's expected vote on the House floor.
The resolution, unveiled earlier this week, lays out procedures for public impeachment hearings, the release of deposition transcripts and outlines the Judiciary Committee's role in considering potential articles of impeachment.
It will be the first full House vote on the impeachment inquiry since Pelosi's initiation of it.
"This resolution does nothing to change the fundamental fact that House Democrats refuse to provide basic due process rights to the Administration," White House press secretary Stephanie Grisham said on Tuesday.
Two State Department officials on Ukraine testified in separate closed-door hearings before the House Intelligence, Oversight and Foreign Affairs committees on Wednesday.
Timothy Morrison, the top Russia and Europe adviser of Trump's National Security Council, who's scheduled to testify on Thursday, is reportedly leaving his job soon.
