The still-secret whistleblower complaint by a member of the U.S. intelligence community concerns President Donald Trump‘s discussions with a Ukrainian leader, according to the Washington Post.

Two sources told the Post that the whistleblower complaint involves an “alarming” promise made by Trump during a conversation with a Ukrainian leader.

Acting Director of National Intelligence, Jospeh Maguire, ignored a congressional subpoena to turn over the contents of the complaint, arguing that the matter concerns someone outside of the U.S. intelligence community.

The Independent reported that House lawmakers are looking into whether Trump asked Ukraine’s president to investigate former vice president and Democratic president candidate Joe Biden, during a July phone call, claiming it would improve relations between the two countries.

Trump denounced the news stories on Twitter, calling it “Fake News.”

He added, “Virtually anytime I speak on the phone to a foreign leader, I understand that there may be many people listening from various U.S. agencies, not to mention those from the other country itself.”

Amid the whistleblower drama, Trump’s personal lawyer, Rudy Giuliani, admitted Thursday that he had asked Ukraine to investigate Biden.

“So you did ask Ukraine to look into Joe Biden?” CNN’s Chris Cuomo asked Giuliani.

“Of course I did,” Giuliani replied.

Former Vice President Joe Biden‘s son, Hunter, is connected to the Ukrainian energy exploration and production company, Bursima Holdings. Giuliani has criticized him for forcing the dismissal of Ukraine’s top prosecutor who was investigating Burisma. An investigation could affect Biden’s campaign, who is currently the Democratic forerunner for the presidential race.

House Intelligence Committee chairman Adam Schiff (D-California) is continuing to push the acting DNI to release the whistleblower complaint to congress.

“The [Intelligence Community Inspector General] determined that the complaint is both credible and urgent, which is why the Committee must move quickly,” said Schiff Thursday. “The Committee’s position is clear — the Acting DNI can either provide the complaint as required under the law, or he will be required to come before the Committee to tell the public why he is not following the clear letter of the law, including whether the White House or the Attorney General are directing him to do so.”

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