Acting Director of National Intelligence Joseph Maguire threatened to resign amid fears the White House wouldn't allow him to share information concerning the whistleblower complaint about President Trump with Congress, The Washington Post reports.

Maguire is set to testify Thursday as questions swirl about the complaint related to Trump's communications with Ukrainian President Volodymyr Zelensky. A partial transcript released Wednesday shows Trump asked Zelensky to investigate former Vice President Joe Biden.

Maguire, the Post reports, "warned the White House that he was not willing to withhold information from Congress" about the whistleblower complaint, and he was essentially "serving notice that he intended to cooperate with lawmakers unless the White House moved forward with a legal case to prevent him from doing so."

The report also says Maguire has been expressing his "displeasure" to White House counsel Pat Cipollone that he's been put "in the untenable position" of having to deny Congress material. Still, the Post reports it's not clear whether Maguire successfully "forced the White House to acquiesce and allow him to testify without constraint."

White House Press Secretary Stephanie Grisham has denied this report, tweeting, "This is actually not true. And we would have gone on the record to say that if the @washingtonpost had given us more than 6 minutes (literally) to respond." Maguire is also now denying the story, in a statement saying, "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."

Ahead of Maguire's testimony, he is reportedly preparing to provide the whistleblower complaint to Congress this afternoon. Brendan Morrow