A U.S. Army officer serving at the National Security Council twice raised concerns over the Trump administration's push to have Ukraine investigate Democrats and Joe Biden, according to testimony the official is prepared to deliver Tuesday in the House impeachment inquiry.

Army Lt. Col. Alexander Vindman, who served in Iraq and, later, as a diplomat, is prepared to tell House investigators that he listened to President Donald Trump's July 25 call with new Ukraine President Volodymr Zelenskiy and reported his concerns to the NSC's lead counsel.

"I was concerned by the call," Vindman will say, according to prepared testimony obtained Monday night by The Associated Press. "I did not think it was proper to demand that a foreign government investigate a U.S. citizen, and I was worried about the implications for the U.S. government's support of Ukraine."

Vindman will be the first current White House official set to appear as the impeachment inquiry reaches deeper into the Trump administration and Democrats prepare for the next, public phase of the probe.

The 20-year military officer will testify that he first reported his concerns after an earlier meeting July 10 in which U.S. Ambassador to the European Union Gordon Sondland stressed the importance of having Ukraine investigate the 2016 election as well as Burisma, a company linked to the family of 2020 Democratic presidential candidate Joe Biden.

Vindman says he told Sondland that "his statements were inappropriate, that the request to investigate Biden and his son had nothing to do with national security, and that such investigations were not something the NSC was going to get involved in or push."

That account differs from Sondland's, a wealthy businessman who donated $1 million to Trump inauguration and testified before the impeachment investigators that no one from the NSC "ever expressed any concerns." He also testified that he did not realize any connection between Biden and Burisma.

For the call between Trump and Zelenskiy, Vindman said he listened in the Situation Room with colleagues from the NSC and Vice President Mike Pence's office, and was concerned. He again reported his concerns to NSC's lead counsel, he said.

He wrote, "I realized that if Ukraine pursued an investigation into the Bidens and Burisma, it would likely be interpreted as a partisan play which would undoubtedly result in Ukraine losing the bipartisan support it has thus far maintained. This would all undermine U.S. national security."

Democrats have indicated they are likely to use no-show witnesses to write an article of impeachment against Trump for obstruction of justice, rather than launching potentially lengthy court battles to obtain testimony.

Navy aircraft were sidelined as they awaited parts last year that the service actually had in a warehouse. The problem? They didn't even know the warehouse was there.

"Not only did we not know that the parts existed, we didn't even know the warehouse existed," Thomas Modly, the Navy's No. 2 civilian said at last week's annual Military Reporters and Editors conference.

The issue was discovered in last year's Navy- and Marine Corps-wide audit, which Modly said has helped the sea services correct some serious problems tracking inventory it owns.

The warehouse in Jacksonville, Florida, auditors found, had about $126 million in aircraft parts for the F-14 Tomcat, P-8 Poseidon and P-3 Orion.

"When they brought those parts into the inventory system, within a couple of weeks there were like $20 million in requisitions on those parts for aircraft that were down because we didn't know we had the parts of the inventory," Modly said.

Tracking inventory is one of the Navy Department's biggest challenges, he added. The Navy and Marine Corps are undergoing efforts to develop a tracking system to "get better data around inventory," he said.

"It's billions of dollars and we don't have good accountability on that," Modly said. "We need to get much better."

The services are also working with vendors that house spare parts for Navy and Marine Corps equipment, he said. The audit showed vendors working with the Navy and Marine Corps often "didn't have visibility into where those things were either," he said.

"They had them and they knew they had them, but there was no way to tie them into a system to be able to go audit [them]," he said. "We've gone back to them and imposed some standards on them this year so that this next year, when we go through this, we think we've got that solved."

Had the Navy Department not done an audit, he said "we never would've known that problem."

Two Army commands responsible for training soldiers will assess whether changes are needed in the wake of a fatal vehicle accident, the service's top civilian leader said.

Officials with Army Forces Command and Army Training and Doctrine Command will review training protocols after three soldiers were killed in Georgia when their Bradley Fighting Vehicle fell from a bridge and landed upside down in a stream on Sunday.

"One of the things we always do is step back and ... do an evaluation," Army Secretary Ryan McCarthy told journalists on Friday at the 2019 Military Reporters and Editors conference outside Washington.

The soldiers killed at Fort Stewart were Sgt. 1st Class Bryan Jenkins, 41, of Gainesville, Florida; Cpl. Thomas Walker, 22, of Conneaut, Ohio; and Pfc. Antonio Garcia, 21, of Peoria, Arizona.

It was one of several recent fatal military vehicle training accidents. A soldier recently faced an Article 32 hearing over his alleged role in a fatal accident that killed a West Point cadet earlier this year.

McCarthy said the Army has been assessing the safety of its training since last fall as part of a review directed by then-Defense Secretary Jim Mattis. Now the Government Accountability Office will also investigate what's behind at least eight Army and Marine Corps training deaths this year, Medill News Service reported on Friday.

The investigation, which was requested by two congressional committees, will look at whether those operating vehicles in recent accidents have been adequately trained and at the mission-capable rates of the equipment, Medill reported.

McCarthy said the Army will support the watchdog agency's investigation.