The White House is considering removing Lt. Col. Alexander Vindman, a key witness in President Donald Trump’s impeachment investigation, as part of a plan to downsize the Trump administration’s foreign policy bureaucracy, according to Bloomberg News.

Vindman serves as the National Security Council’s expert on Ukraine affairs and listened in on the July 25 telephone between President Trump and Ukrainian President Volodymyr Zelensky, in which the president asked his counterpart to look into allegations of corruption against former Vice President Joe Biden and his son, Hunter Biden.

The call prompted a partisan CIA officer to file a whistleblower complaint, which served as the basis for the House Democrats’ formal impeachment probe. Vindman has been accused of leaking details of the call to the whistleblower. RealClearPolitics reported the whistleblower is suspected to be the CIA’s Eric Ciaramella.

Testifying before the House Intelligence Committee in October, Vindman claimed he does not know the identity of the whistleblower. Appearing before lawmakers, Vindman accused President Trump of undermining U.S. national security interests in the summer call.

“I did not think it was proper to demand that a foreign government investigate a U.S. citizen, and I was worried about the implications for the U.S. government’s support of Ukraine,” Vindman said.

“I realized that if Ukraine pursued an investigation into the Bidens and [gas company] Burisma, it would likely be interpreted as a partisan play, which would undoubtedly result in Ukraine losing the bipartisan support it has thus far maintained,” he continued.

“This would all undermine U.S. national security,” he added. “Following the call, I again reported my concerns to NSC’s lead counsel.”

Top Republicans, including President Trump, slammed Vindman’s testimony, branding him as a “Never Trumper” and dismissing his account of the call.

“Was he on the same call that I was? Can’t be possible! Please ask him to read the transcript of the call,” the president wrote on Twitter.

Sen. Marsha Blackburn (R-TN) wrote: “Alexander Vindman broke the chain of command and leaked the contents of the President’s July 25th phone call to his pal, the ‘whistleblower.’ Over a policy dispute with the President! How is that not vindictive?”

Reacting to Bloomberg News’ report, Rep. Thomas Massie (R-KY) called on Vindman to be fired, calling him a leaker.

“Vindman was upset that @realDonaldTrump didn’t follow the script Vindman prepared for the phone call. Current Commander in Chief doesn’t take orders from a Lt. Col.!” wrote Massie.

Although Vindman has denied knowing the whistleblower, the NSC staffer did tell the House Intelligence panel that he discussed the Trump-Zelensky call with his twin brother, Yevgeny. “A source close to the Trump administration informs Breitbart News that Army Lt. Col. Yevgeny Vindman, a senior ethics lawyer for the National Security Council (NSC), is in charge of reviewing all publications by current and former NSC officials,” Breitbart News reported.

There are no reported plans to remove Yevgeny from his post at this time.