(CNN) A career attorney for the Office of Management and Budget plans to testify behind closed doors for the impeachment inquiry should he receive a subpoena, his attorney told CNN on Thursday.

Mark Sandy, who has worked for the Office of Management and Budget for both Republican and Democratic presidents, is scheduled for testimony on Saturday. He served as acting director at OMB in January and February 2017.

"If he is subpoenaed he will appear for the deposition," said Barbara "Biz" Van Gelder, his attorney.

It would be the first time an official from the agency, which was responsible for releasing the security aid for Ukraine, would testify in the impeachment inquiry after multiple other officials ignored subpoenas. The security aid for Ukraine is at the center of the impeachment probe, as multiple officials have reported the aid was blocked to get Ukraine to take up investigations that would have benefited President Donald Trump's domestic political agenda.

Van Gelder said Sandy has not received a subpoena yet. The practice so far during the impeachment inquiry has been that the House committees deliver the subpoena on the morning of the day of scheduled testimony.

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