By Andrew Duehren 

WASHINGTON -- House impeachment investigators are set to hear from a top career White House budget staffer behind closed doors on Saturday as the probe examines why nearly $400 million in aid to Ukraine this summer was held up.

Mark Sandy, deputy associate director for national-security programs at the Office of Management and Budget, signed paperwork initially holding up the aid on July 25, according to previous testimony to impeachment investigators. He didn't appear for a deposition initially scheduled for last week. Barbara Van Gelder, a lawyer representing Mr. Sandy, said he would appear on Saturday if he was subpoenaed.

Before he signed off on the hold, Mr. Sandy sought an opinion from OMB lawyers about the legality of the move, according to people familiar with the matter. After he received legal guidance that the hold could go forward, Mr. Sandy signed the paperwork, according to the people. Lawyers from OMB are often involved in complicated budgeting maneuvers.

The House impeachment inquiry, which began holding public hearings Wednesday, is investigating whether or not the freeze on the aid was conditioned on President Trump's request for Ukraine to investigate former Vice President Joe Biden and 2016 election interference. Mr. Trump has repeatedly denied that his request for the investigations was related to the freeze on the funds.

A senior administration official played down the significance of Mr. Sandy's appearance.

"Democrats are going to be sorely disappointed when their latest false narrative isn't confirmed," the official said.

Mr. Sandy, the first official from OMB to appear before impeachment investigators, may reveal more details about how the aid was held up and why it was ordered. Several political officials from OMB, including acting director Russ Vought, have defied subpoenas to appear. The White House has sought to prevent administration officials from cooperating with the investigation.

The order to hold the funds caught national-security officials at several agencies off guard when it was first announced at a July 18 meeting. Several officials have testified that the legality of the hold was discussed repeatedly at a series of meetings in July.

The Government Accountability Office, Congress's nonpartisan watchdog, is reviewing whether the hold followed legal procedures for freezing the money. The administration ultimately released the funds on Sept. 11 amid bipartisan pressure on Capitol Hill.

Michael Duffey, the associate director for national-security programs at OMB, began carrying out the hold on the money in August after officials began raising concerns about the legality of the hold, according to people familiar with the matter and transcripts of impeachment depositions.

Mr. Duffey, a political appointee and former executive director of the Wisconsin Republican Party who began at OMB in May, began signing the paperwork because he wanted more insight into OMB's role, according to people familiar with his change. He also began directly overseeing holding and releasing other foreign aid and defense funds.

Mr. Duffey, also a former Pentagon official, didn't comply with a congressional subpoena for his testimony this month.

Several former OMB officials have said that a political appointee signing the paperwork for releasing funds is unusual and breaks from precedent at the organization.

Write to Andrew Duehren at andrew.duehren@wsj.com

(END) Dow Jones Newswires

November 16, 2019 06:14 ET (11:14 GMT)