WASHINGTON (AP) — White House officials sought to "lock down" records of a phone call in which President Donald Trump urged his Ukrainian counterpart to investigate Democratic rival Joe Biden, according to a secret whistleblower complaint made public Thursday.

The document was released ahead of scheduled testimony from Joseph Maguire, the acting director of national intelligence.

House Democrats who are now mulling Trump's impeachment are hoping Maguire will explain why he withheld the intelligence community whistleblower's complaint from Congress for weeks. Maguire will then go behind closed doors to speak to the Senate intelligence panel.

Lawmakers have been given a redacted, declassified version of the complaint that can be made public.

The complaint is at least in part related to the July phone call between Trump and Ukrainian President Volodymyr Zelenskiy in which Trump prodded Zelenskiy to investigate former Vice President Biden. The White House released a rough transcript of that call Wednesday morning.

House Speaker Nancy Pelosi on Tuesday endorsed an impeachment investigation in light of the Ukraine revelations.