Sandy, a career official of the Office of Management and Budget, would be the first person from OMB to testify before the inquiry after three political appointees defied congressional subpoenas to appear.
Earlier this week, Sandy's lawyer said his client would appear for a deposition if he is issued a subpoena. It remained unclear on Saturday whether a subpoena was issued.
Trump's pressure on Ukraine is at the heart of the Democratic-led inquiry into whether the Republican president misused US foreign policy to undermine one of his potential opponents in the 2020 election.
On Friday, Trump launched a Twitter attack on a former US ambassador to Ukraine while she was testifying to an impeachment hearing in Congress, in an extraordinary moment that Democrats said amounted to witness intimidation.
Trump blasted Marie Yovanovitch, a career diplomat, as she explained to the second day of televised impeachment hearings how she had fought corruption in Ukraine and how the Trump administration abruptly removed from her post earlier this year.