drnadig/iStock(WASHINGTON) — Two White House national security aides who expressed concerns about a July phone call between President Donald Trump and Ukraine’s leader are appearing on Capitol Hill Tuesday, becoming the first current White House officials to testify publicly in the Democrats’ impeachment investigation.

Army Lt. Col. Alexander Vindman, the National Security Council’s Ukraine expert, will testify alongside Jennifer Williams, a national security aide to Vice President Mike Pence, in the morning.

Both officials listened in on Trump’s July 25 phone call with Ukrainian President Volodymyr Zelenskiy. Vindman and Williams have also come under attack from the president for offering their accounts to Congress.

Here is how the hearing is unfolding. Please refresh for updates.

10:13 a.m.

ABC News’ Mary Bruce notes that Vindman is contradicting the White House readout of the April 21 call between Presidents Trump and Zelenskiy.

“Vindman says his talking points encouraged the president to raise the issue of corruption. At the time, the White House readout of the call said the issue came up. But Vindman notes the president never actually raised the issue. And the transcript that the White House released last week shows it was not brought up,” Bruce says.

Vindman testified that he was on that call and that corruption was part of the National Security Council recommended talking points for the president, but that he does not recall the issue of corruption coming up on the call.

10:03 a.m.

In describing President Trump’s asking Ukraine’s leader to launch investigations that may help his 2020 reelection effort, Vindman relayed his experience in the military to describe why he understood Trump’s overture as “an order,” not a “request.”

“Chairman, the culture I come from – the military culture – when a senior asks you to do something, even if it’s polite and pleasant, it’s not to be taken as a request. It’s to be taken as an order,” Vindman said.

“In this case, the power disparity between the two leaders, my impression is that in order to get the White House meeting, President Zelenskiy would have to deliver these investigations.”

ABC News Political Director Rick Klein tweets this analysis: “A key point that the witnesses last week made too — that a ‘favor’ is more like a demand in light of Ukraine’s reliance on the US.”

10:01 a.m.

Both Vindman and Williams say they remember hearing the word “Burisma” on the July 25 phone call, but that it was omitted in the transcript. “It’s not a significant omission,” Vindman said, but said he tried to correct the record. Burisma is not mentioned in the transcript released by the White House.

Burisma is the gas company in Ukraine that hired Hunter Biden to sit on its board.

9:47 a.m.

Vindman, delivering his opening statement in his U.S. Army uniform, pushes back on criticisms brought forth by the president’s allies, insisting his role in the impeachment inquiry comes not from bipartisan bias, but “under a common oath to protect and defend the Constitution of the United States of America.”

“We do not serve any particular political party, we serve the nation. I am humbled to come before you today as one of many who serve in the most distinguished and able military in the world,” Vindman says.

On Monday, Sen. Ron Johnson, R-Wisc., suggested Vindman was a “bureaucrat” who “never accepted President Trump as legitimate and resent his unorthodox style,” and indirectly accused him of “leaking to the press and participating in the ongoing effort to sabotage his policies.”

Vindman notes his brother is in the audience and then directs his testimony at his father, who fled the Soviet Union 40 years ago and brought Vindman and his brother to the United States.

Vindman said he and his siblings chose public service to repay the country that took them in. Vindman also notes that his actions, if in Russia, would have “surely cost me my life.” Then he assured his father “do not worry, I will be fine for telling the truth.”

9:38 a.m.

Williams gives her opening statement first, defending her service in the U.S. diplomatic corps after President Trump targeted her on Twitter over the weekend.

“As a career officer, I am committed to serving the American people and advancing American interests abroad, in support of the President’s foreign policy objectives,” Williams said Tuesday.

“I found the July 25th phone call unusual, because in contrast to other presidential calls I had observed, it involved discussion of what appeared to be a domestic political matter.”

9:22 a.m.

Ranking Member Devin Nunes blamed media coverage of the hearings last week for overstating the impact of last week’s testimony and continued calls for more information about the whistleblower whose complaint launched the impeachment inquiry.

Schiff has said he does not know the identity of the whistleblower and will protect them from being publicly identified due, in part, to security concerns.

9:17 a.m.

The president has called both witnesses “Never Trumpers.”

Schiff notes the attacks on Williams and Vindman.

“Ms. Williams, we all saw the President’s tweet about you on Sunday afternoon and the insults he hurled at Ambassador Yovanovich last Friday. You are here today, and the American people are grateful,” Schiff says. “Col. Vindman, we have seen far more scurrilous attacks on your character, and watched as certain personalities on Fox have questioned your loyalty. I note that you have shed blood for America, and we owe you an immense debt of gratitude.”

9:09 a.m.

House Intelligence Committee Chairman Adam Schiff opens the hearing by reviewing what other witnesses have testified, saying President Donald Trump has “placed his own personal and political interests above those of the nation.”

Vindman and Williams are sitting side-by-side at the witness table as Schiff introduces them as having been alarmed by the July 25 call.

9:01 a.m.

ABC News Senior Congressional Correspondent Mary Bruce notes that today’s witnesses provide some of the testimony that prompted the impeachment inquiry by raising concerns about the administration’s dealings in Ukraine.

“Today we are going to be hearing from witnesses who were on that phone call that sparked this entire impeachment inquiry and they have described what they heard as unusual and inappropriate,” Bruce says.

8:45 a.m.

Jennifer Williams has arrived as well. She will be today’s first witness. The hearing room is filling up quickly with congressional staff, reporters and spectators.

Tuesday’s hearing starts off an important week in the impeachment inquiry after the first two days of public testimony last week.

If you missed last week’s hearings you can catch up on some of the key takeaways from former U.S. ambassador to Ukraine Marie Yovanovitch and the first hearing with William Taylor, the top U.S. diplomat in Ukraine, and George Kent, the State Department’s top career official tasked with Ukraine policy.

8:15 a.m.

Army Lt. Col. Alexander Vindman has arrived in Capitol Hill in his dress blue uniform. He was accompanied by his brother, Yevgeny, who is also serves on the National Security Council as an ethics lawyer.

Vindman told investigators, according to a transcript of his closed session, that he was “concerned” by the call, adding that he “did not think it was proper to demand that a foreign government investigate a U.S. citizen,” a reference to the suggestion from Trump that Ukraine investigate former Vice President Joe Biden’s son, Hunter Biden, and his work for Ukrainian energy company Burisma. He also told lawmakers there was “no doubt” in his mind about what Trump sought from Ukraine in the July phone call with Zelenskiy.

In his private testimony, Vindman also told lawmakers he repeatedly raised his concerns about the president’s comments — along with the discussion of the investigations that Rudy Giuliani, Trump’s personal lawyer, was publicly calling for — with NSC lawyers.

He also said he attempted to get nearly $400 million in military aid to Ukraine restored after it was put on hold over the summer, drafting a memo that the president refused to sign.

The Iraq War veteran, who received a Purple Heart, is expected to appear in uniform.

Williams said in a separate closed session with lawmakers that she found the mention of investigations into the 2016 election and unsubstantiated theories of Ukraine’s meddling in the race, and a probe into the Biden family’s dealings in Ukraine “unusual and inappropriate.”

The president has lashed out at both officials, calling Vindman a “never Trumper” as he testified to Congress last month, and criticizing Williams after her closed-door testimony was released over the weekend.

Tim Morrison, a departing NSC official who was also on the Trump-Zelenskiy call, will testify Tuesday afternoon. While he raised concerns about the call to White House lawyers — specifically, how a leak of the transcript would be received in a polarized Washington, and impact bipartisan support for Ukraine — he previously told impeachment investigators that he was “not concerned that anything illegal was discussed,” according to a transcript of his deposition released by House Democrats.

Lawmakers will also question former U.S. envoy to Ukraine Kurt Volker on Tuesday afternoon.

Republicans, who requested the public testimony from both officials, believe elements of their accounts undermine Democrats’ concerns about the withholding of aid for investigations at the center of the impeachment inquiry.

Tuesday’s testimony could set the stage for the upcoming appearance of Gordon Sondland, Trump’s ambassador to the European Union and an apparent central player in the efforts to encourage Ukraine to launch investigations that could benefit Trump politically.

The House Intelligence Committee is scheduled to hold a total of five public hearings this week with nine witnesses.

Sondland will testify Wednesday morning, followed by senior Defense Department and State Department officials Laura Cooper and David Hale.

Fiona Hill, the NSC’s former Russia expert under former national security adviser John Bolton, is scheduled to appear on Capitol Hill Thursday morning, along with Holmes.

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