Michael McKinley, a former top aide to Secretary of State Mike Pompeo Michael (Mike) Richard PompeoWatchdog confirms State Dept. canceled award for journalist who criticized Trump Trump's push for win with Sudan amps up pressure on Congress Putin nominated for Nobel Peace Prize MORE, is reportedly set to testify Wednesday as part of House Democrats’ impeachment inquiry.

CNN reports McKinley’s expected testimony comes just a week after he resigned as a senior adviser to Pompeo.

Two congressional sources told the network that McKinley will appear before the House Intelligence, Oversight and Reform and Foreign Affairs committees.

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McKinley held the role as a top aide to Pompeo since May 2018 after previously serving as a U.S. ambassador to Peru, Colombia, Afghanistan and Brazil.

He is appearing before the House committees for a transcribed interview, one of the sources told CNN, indicating that he was not subpoenaed.

McKinley was reportedly concerned with the handling within the State Department following Marie Yovanovitch's exit as U.S. ambassador to Ukraine, with a source telling CNN it was one reason behind his departure. The source added that McKinley had been considering leaving his post for a few weeks.

McKinley is the latest official from the State Department to testify before House committees as investigators look into how the department dealt with the Ukraine scandal as part of Democrats’ impeachment inquiry into President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE. Revelations that Trump pressured Ukraine's president to investigate former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE, a leading 2020 presidential candidate, and his son sparked the inquiry. No evidence of criminal wrongdoing by the Bidens has emerged.

A former State Department official added that McKinley is "known to be a man of integrity, a man of principle."

"If he had encountered something either that was happening in the State Department or he felt he could no longer carry out his duties without compromising his integrity and his principles, he is somebody who would feel he had no choice but to resign," the source told CNN.

McKinley’s exit comes after 37 years with the State Department, he told colleagues in a letter last week announcing his departure.

He declined to comment to CNN on his upcoming testimony.