The whistleblower complaint that reportedly centers on President Donald Trump and his interactions with Ukraine has been declassified, sources familiar with the matter told NBC News on Wednesday night.

The complaint, which the administration initially withheld from Congress, was declassified with what were described as minimal redactions, the sources said, and there is an expectation that it will be released Thursday morning.

It is thought to be related to a July phone call between Trump and Ukrainian President Volodymyr Zelenskiy.

The details have not been made public, though it has widely been reported that the complaint involves Trump, funding for Ukraine and an attempt to get information about former Vice President Joe Biden and his family. The complaint is at the center of a standoff between the White House and Congress that led to a formal impeachment inquiry against Trump.

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The White House has not responded to the reported declassification of the complaint.

The complaint was released to Congress on Wednesday, and Democrats who read it described it as containing important new information, even though they couldn't discuss what the information was.

House Intelligence Committee Chairman Rep. Adam Schiff, D.-Calif, said Wednesday the allegations in the complaint were "very credible" and "deeply disturbing.”

"The complaint is very well written, and certainly provides information for the committee to follow up with other witnesses and documents," he said.

The complaint was filed last month by the acting inspector general for Director of National Intelligence, who found it to be "credible" and "urgent." It was supposed to be turned over to Congress within a week, but acting Director of National Intelligence Joseph Maguire refused to do so on the advice of the Justice Department. Maguire is set to testify publicly before the House Intelligence Committee Thursday morning.

The whistleblower has not been identified. The legal team representing the whistleblower, who they say is a member of the intelligence community, said they welcomed its release.

“We applaud the decision to release the whistleblower complaint as it establishes that, ultimately, the lawful whistleblower disclosure process can work,” attorneys Andrew P. Bakaj, I. Charles McCullough III and Mark S. Zaid said in a statement. “We await the release of the complaint in its totality,” the attorneys said.

Earlier Wednesday, the White House released a description of the call between Trump and Zelenskiy that showed Trump asked him to look into why that country's top prosecutor apparently had ended an investigation of the business dealings of Joe Biden’s son, who served on the board of a Ukrainian gas company.

Trump said Wednesday that he applied "no pressure whatsoever" in his phone call with Ukraine’s president. He said it was "friendly" and that the media built it up to be the "call from hell" and it turned out to be "nothing."

Democrats widely expressed outrage over the contents of the description of the phone call released by the Trump administration.

Biden, who is running for the 2020 Democratic presidential nomination, said Trump "put personal politics above his sacred oath" and accused the president of having "put his own political interests over our national security interest, which is bolstering Ukraine against Russian pressure."

The White House noted that the summary of the call was not a verbatim transcript and that it represented a record of "the notes and recollections of Situation Room Duty officers and National Security Council policy staff" who listen to official conversations.