LIVE: Acting DNI Joseph Maguire is about to testify to Congress about an explosive whistleblower complaint against Trump

Nicholas Kamm/Reuters

Acting DNI Joseph Maguire.

• Acting director of national intelligence Joseph Maguire is gearing up to testify before the House Intelligence Committee in an explosive hearing about President Donald Trump's alleged misconduct while in office.
• Maguire will testify about the contents of an unprecedented whistleblower complaint against Trump, which details a July 25 phone call in which Trump repeatedly pressured Ukrainian President Volodymyr Zelensky to investigate former Vice President Joe Biden ahead of the 2020 election.
• Maguire and the intelligence community inspector general, Michael Atkinson, referred the complaint to the Justice Department for a criminal investigation, but the department decided not to launch a probe.
• Lawmakers will likely ask Maguire about his communications with the White House and the Justice Department about the matter, as well as other details contained within the complaint, which was expected to be released Thursday morning.
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This story will be updated as Maguire testifies.

The acting director of national intelligence, Joseph Maguire, is getting ready to testify before Congress about an explosive and unprecedented whistleblower complaint against President Donald Trump.

Maguire is set to appear before the House Intelligence Committee at 9 a.m. ET in an open hearing.

He turned the complaint over to Congress on Wednesday. The move came after a fierce tug-of-war in which Maguire, after consulting with the Justice Department and White House, determined he was not required to hand over the complaint because the person it related to - Trump - was not within the DNI's jurisdiction.

The Washington Post reported on Wednesday that Maguire was unhappy with White House counsel Pat Cipollone and other officials over the decision, and that he threatened to resign if the White House tried to block him from testifying before the House Intelligence Committee on Thursday.

But Maguire disputed the Post's reporting, saying in a statement Wednesday: "At no time have I considered resigning my position since assuming this role on Aug. 16, 2019. I have never quit anything in my life, and I am not going to start now."

Read more: Ukrainian officials say Trump would only talk to Zelensky 'if they would discuss the Biden case' in their July phone call

Jonathan Ernst/Reuters

President Donald Trump meets with with Ukraine's President Volodymyr Zelensky at the United Nations General Assembly in New York City on September 25, 2019.

The whistleblower's complaint will take the spotlight at Maguire's hearing. Lawmakers will likely ask him about his communications with the Justice Department and the White House on the matter, as well as additional details about a July 25 phone call Trump had with Ukrainian president Volodymyr Zelensky, which is at the heart of the whistleblower complaint.

Trump had ordered his administration to withhold a nearly $400 million military-aid package to Ukraine days before the phone call.

While the White House's notes of the call show the US president made no direct mention of offering aid in exchange for Zelensky's assistance in probing former Vice President Joe Biden, they confirm Trump brought up how the US does "a lot for Ukraine" right before asking Zelensky to do him a "favor" by investigating Biden and discrediting the former special counsel Robert Mueller's Russia probe.

On Tuesday, it surfaced that Maguire and the intelligence community inspector general, Michael Atkinson, referred the complaint to the Justice Department for criminal investigation because Atkinson believed Trump may have violated campaign finance laws during his phone call with Zelensky and that the matter posed a threat to US national security.

But the Justice Department's criminal division reviewed the whistleblower's complaint and determined that there were no grounds for an investigation of Trump's behavior, The New York Times reported. Officials are said to have decided that the memo of Trump's phone call with Zelensky didn't show him violating campaign finance laws by asking for a financial contribution or an "item of tangible value."

House Speaker Nancy Pelosi announced an impeachment inquiry into Trump on Tuesday over the phone call.

Watch a livestream of the hearing below: