Two staffers for the Office of Management and Budget (OMB) resigned after expressing frustrations about a hold on military assistance to Ukraine that is now at the center of the impeachment inquiry, a witness has testified.

Mark Sandy, an OMB staffer, testified this month that the two staffers, one of whom was in the legal division, had resigned partially due to frustrations with the unexplained aid freeze, according to a transcript of his testimony released Tuesday. 

Sandy recalled that one individual who resigned had "expressed some frustrations about not understanding the reason for the hold," according to the transcript, but he noted that he was "reluctant to speak to someone else's motivations."

He was also asked whether the OMB legal division employee said they were leaving "at least in part because of their concerns on frustrations about the hold on Ukraine security assistance."

"Yes, in terms of that process, in part," Sandy responded.

The officials were not named in the transcript.

A senior administration official categorized the assertion that the two officials resigned in part over the aid freeze as false in an email to The Hill.

Sandy also testified that he believed President TrumpDonald John TrumpTrump puts Kushner in charge of overseeing border wall construction: report Trump 2020 national spokesperson gives birth to daughter New McCarthy ad praising Trump includes Russian stock footage MORE had directed the hold on Ukraine aid.

His testimony was part of the House's impeachment inquiry into Trump's dealings with Ukraine, including the freeze on security assistance.

The transcript of Sandy's closed-door interview was one of the latest released by House Democrats. They also released testimony from a closed-door session with Philip Reeker, the acting assistant secretary of State in charge of European and Eurasian Affairs.

House Intelligence Committee Chairman Adam SchiffAdam Bennett SchiffNunes faces potential ethics review over alleged meeting with Ukrainian official Poll: Interest in impeachment inquiry dips among Democratic voters Schiff: Judiciary Committee to receive impeachment report 'soon after' Thanksgiving recess MORE (D-Calif.), Oversight and Reform Committee Chairwoman Carolyn MaloneyCarolyn Bosher MaloneyThe Hill's Morning Report - Sondland stuns; Dems pull punches in fifth debate Maloney wins House Oversight gavel The Hill's Morning Report - Wild Wednesday: Sondland testimony, Dem debate take center stage MORE (D-N.Y.), and Foreign Affairs Committee Chairman Eliot EngelEliot Lance EngelOvernight Defense — Presented by Boeing — House chairmen demand answers on Open Skies Treaty | China warns US to stay out of South China Sea | Army conducting security assessment of TikTok House chairmen demand answers on surveillance flight treaty Maloney wins House Oversight gavel MORE (D-N.Y.) said in a statement Tuesday that the Reeker and Sandy interviews bolster their case against Trump. 

"The testimonies from Ambassador Reeker and Mr. Sandy continue to paint a portrait of hand-picked political appointees corrupting the official levers of U.S. government power, including by withholding taxpayer funded military assistance to Ukraine, to further the President’s own personal political agenda," they said.

Hours after Democrats released the transcripts, Trump appeared at a campaign rally in Florida, where he blasted the ongoing impeachment inquiry, with supporters breaking into a chant of "bullshit" when he insisted that the inquiry was falling flat with voters.

The transcripts' release comes as Schiff's panel works to put together a report for the Judiciary Committee that will be used to determine whether to draft articles of impeachment against Trump. 

The House launched the inquiry after revelations that Trump had asked Ukraine's president to look into former Vice President Joe BidenJoe BidenKennedy walks back comments on potential Ukraine interference: 'I was wrong' Nunes faces potential ethics review over alleged meeting with Ukrainian official Bloomberg campaign chief: Trump is winning 2020 election right now MORE, a top political rival and leading candidate for the 2020 Democratic presidential nomination.

Updated: 10 p.m.