A top official at the U.S. Embassy in Ukraine told impeachment investigators he had "never seen anything like" the late July phone conversation he overheard between President Donald Trump and his ambassador to the European Union, Gordon Sondland, in a Kyiv restaurant.

"This was an extremely distinctive experience in my Foreign Service career," David Holmes, the counselor for political affairs at the U.S. Embassy in Ukraine, said in a deposition Friday, according to a transcript released late Monday. "I've never seen anything like this, someone calling the president from a mobile phone at a restaurant, and then having a conversation of this level of candor, colorful language. There's just so much about the call that was so remarkable that I remember it vividly."

The call Holmes is referencing is one first brought up by the top U.S. diplomat in Ukraine, Bill Taylor, during last week's public testimony. Taylor said one of his staffers, later revealed to be Holmes, overheard a phone call on July 26 during which Trump asked Sondland about "the investigations," meaning the probes into the Bidens and Democrats.

Holmes, who is now slated to appear for public testimony Thursday, told impeachment investigators he heard Sondland tell Trump that Ukrainian President Volodymyr Zelenskiy "loves your ass," to which Trump asked, "So, he's gonna do the investigation?" Sondland replied that Zelenskiy was "gonna do it," adding that the Ukrainian leader would do "anything you ask him to."

Holmes said he was able to make out what Trump was saying during that brief portion of the phone call because Sondland held the phone away from his ear as Trump was speaking loudly. Holmes would testify that Trump's unmistakable voice was later quieter. Holmes said he did not take notes of that part of the call but told fellow embassy staffers what he heard.

"I then took the opportunity to ask Ambassador Sondland for his candid impression of the president’s views on Ukraine," Holmes said. "In particular, I asked Ambassador Sondland if it was true that the president did not give a shit about Ukraine. Ambassador Sondland agreed that the president did not give a shit about Ukraine."

"I asked why not, and Ambassador Sondland stated, the president only cares about 'big stuff,'" Holmes continued. "I noted that there was 'big stuff' going on in Ukraine, like a war with Russia. And Ambassador Sondland replied that he meant 'big stuff' that benefits the president, like the 'Biden investigation' that" Trump's personal attorney Rudy Giuliani "was pushing."

Sondland, who did not mention this call in either his initial October deposition and or in subsequent written testimony he gave this month, will appear publicly before impeachment investigators on Wednesday.

Additionally, Holmes testified that because Russian companies own or have a significant stake in most of the cell phone companies in the country, "We generally assume that mobile communications in Ukraine are being monitored."

Holmes, who said he is not "engaged in U.S. politics in any way," also said the allegations directed at ousted U.S. Amb. Marie Yovanovitch were "unlike anything I've seen in my professional career." He also testified that he recalled Sondland once saying of Giuliani's media push to elevate allegations involving Democrats and Ukraine: "'Dammit, Rudy. Every time Rudy gets involved he goes and effs everything up.' He used the 'F' word."

As for why he came forward, Holmes said as he "saw the story coming out and then started hearing that there was not a lot of firsthand information, plus the notion that these three officials" — Sondland, Energy Secretary Rick Perry and then-special representative to Ukraine Kurt Volker — "that were close officials to the president may have been acting without his knowledge or freelancing."

"It seemed to be then, in retrospect, that this [phone call] even was firsthand and one of those people with direct contact to the president, where they explicitly mentioned one of the things that was at issue," Holmes added. "In retrospect, it seemed like it was more critical."

Impeachment investigators are digging into allegations that Trump leveraged the presidency and withheld roughly $400 million in military aid to Ukraine until Zelenskiy publicly announced probes of the Bidens and a debunked conspiracy theory regarding Democrats and the 2016 election. The probe started after a whistleblower, a CIA employee, filed a formal complaint alleging that Trump was seeking foreign interference from Ukraine in the 2020 election. The White House released a summary of Trump's July 25 call with Zelenskiy in which the president asked his counterpart for a "favor" and mentioned both investigations.

Republicans have contended that because the aid was delivered to Ukraine without any investigations being announced, Trump's conduct is not impeachable. Trump released the aid on Sept. 11, two days after Congress was alerted to the whistleblower complaint.

"Having this all come out into public has weakened that relationship and exposed things that didn't need to be exposed," Sen. Ron Johnson, R-Wisc., told NBC's "Meet the Press" on Sunday of the information made public by the whistleblower's complaint, adding, "This would have been far better off if we would have just taken care of this behind the scenes."

Trump's allies have also said that Ukraine was unaware of the military aid being tied to such investigations. But in his testimony, Holmes said, "I think the Ukrainians gradually came to understand that they were being asked to do something in exchange for the [White House] meeting and the security assistance hold being lifted."