Army Lt. Col. Alexander Vindman, a military officer at the National Security Council, center, arrives on Capitol Hill in Washington on Tuesday to appear before a House Committee on Foreign Affairs, Permanent Select Committee on Intelligence, and Committee on Oversight and Reform joint interview with the transcript to be part of the impeachment inquiry into President Donald Trump. Credit: Patrick Semansky | AP

WASHINGTON — National Security Council Ukraine expert Lt. Col. Alexander Vindman’s testimony in the House impeachment probe Tuesday is shedding new light on how Trump administration officials pressured Ukrainian leaders into investigations that could benefit the president, corroborating other witnesses with a firsthand account of the alleged attempt at a quid pro quo.

Vindman’s prepared remarks directly challenge the testimony of U.S. Ambassador to the European Union Gordon Sondland, who defended the president’s actions and told House investigators that no one had raised concerns about them. Sondland told the top American diplomat in Ukraine, Ambassador William Taylor, in September text messages saying Trump had not engaged in a quid pro quo; those text messages were provided to investigators by former special U.S. envoy to Ukraine Kurt Volker earlier this month.

Taylor’s testimony from last week, which laid out in meticulous detail how a shadow Ukraine policy involving Sondland and directed by Trump’s lawyer Rudy Giuliani prioritized investigating Trump’s political rivals over U.S. national security interests, has been held up as the most incriminating to date. But Vindman’s recollections, while narrower, illuminate key episodes in Taylor’s narrative with an even closer perspective: Vindman was either in the room or briefed personally after meetings by the Trump administration officials involved in exchanges Democrats believe amounted to a quid pro quo.

Vindman is the first witness in the House’s impeachment probe to have not only listened in on the July 25 call between Trump and Ukrainian President Volodymyr Zelensky, in which Trump said he wanted a “favor” after Zelensky brought up the topic of promised American military aid. Vindman was listening in from the Situation Room, he said, along with other NSC officials and members of Vice President Mike Pence’s office, and was so “concerned by the call” — and that the president’s request could be seen as “a partisan play” that could “undermine U.S. national security” — that he reported it to the NSC’s lead counsel.

Vindman’s prepared testimony touched a nerve with Trump, who took to Twitter on Tuesday to deride the Iraq War veteran, who appeared for his testimony in uniform, as a “Never Trumper,” questioning his recollection of events.

“Supposedly, according to the Corrupt Media, the Ukraine call ‘concerned’ today’s Never Trumper witness. Was he on the same call that I was? Can’t be possible!” Trump wrote on Twitter. “Please ask him to read the Transcript of the call. Witch Hunt!”

Vindman also went to the NSC’s lead counsel with concerns about a July 10 meeting between Sondland, Volker, Energy Secretary Rick Perry, then-national security adviser John Bolton and senior Ukrainian officials. During the meeting, according to Vindman’s prepared statement, Sondland demanded that Ukrainian leaders deliver “specific investigations” to secure a meeting between Zelensky and Trump.

Vindman said he was told about that meeting directly by Sondland himself in the immediate aftermath of the event, according to his prepared remarks. During the previously scheduled debrief, “Sondland emphasized the importance that Ukraine deliver the investigations into the 2016 election, the Bidens, and Burisma,” Vindman’s prepared testimony reads.

“I stated to Amb. 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,” Vindman adds.

Sondland is already under pressure from some lawmakers to return to Capitol Hill due to other discrepancies between his testimony and that of others like Taylor, who told investigators that Sondland was aware that Trump was leveraging a meeting and, later, almost $400 million in congressionally-approved military aid for Ukraine on promises to conduct investigations.

Tim Morrison, the NSC official who told Taylor that Ukraine’s military aid was being held up to secure investigations into former vice president Joe Biden’s son Hunter’s role on the board of Ukrainian energy company Burisma, as well as a debunked conspiracy theory involving a Democratic National Committee that was hacked in 2016, is expected to testify in the impeachment inquiry on Thursday.

Sondland appeared to demur during his closed-door deposition earlier this month about whether believed that almost $400 million in military aid for Ukraine was being withheld to secure the investigations. But in recent days, Sondland’s lawyer, Robert Luskin, has told the Wall Street Journal that his client believes — and told House investigators — that Trump’s refusal to meet with Zelensky until the Ukrainians promised to launch the investigations amounted to a quid pro quo.

Vindman’s prepared testimony does not address whether military aid was being withheld to secure U.S. elections; it just stresses that Sondland held back the promise of a phone call between the two heads of state until Ukraine pledged to conduct the investigations.

Sondland appeared on Capitol Hill again on Monday to review the transcript of his previous testimony in a secure facility, a courtesy afforded to all interviewees.

Vindman’s testimony also raises new questions about the role that Bolton and his other senior deputies may play in the investigation as it proceeds. Bolton was furious by Sondland’s demands of the Ukrainians during the July 10 meeting, according to Vindman’s testimony and that of former NSC senior director for Russia and Europe Fiona Hill. Hill testified earlier this month that Bolton thought Giuliani was a “hand grenade” and wanted it known that he would not participate in a Ukraine policy that he likened to a “drug deal” between Sondland and acting White House chief of staff Mick Mulvaney, who had convened the meeting.

The panels have thus far not subpoenaed Bolton for his testimony, though many Democrats believe he could be a powerful and incriminating witness against the president in a public hearing. But Bolton shares a lawyer with his former top deputy, Charles Kupperman, who petitioned the courts late last week to rule on whether he must comply with a congressional subpoena to testify in the impeachment probe.

Democrats, who are committed not to slow their probe by getting into protracted legal battles, have rejected Kupperman’s filing as legally baseless, with House Intelligence Committee Chairman Rep. Adam Schiff, D-California, predicting Monday that the courts would “make short shrift” of the argument and force Kupperman to go before the panel.

That may happen sooner than initially appeared. A federal judge said Monday that he wanted to hear from lawyers for the House, Kupperman and the Trump administration on Thursday afternoon.