Alex Wong/SAUL LOEB/AFP via Getty Images
Now playing
02:28
Key diplomat's transcript released as Pence aide testified
US President Donald Trump speaks during a "Make America Great Again" rally at the Eastern Kentucky University, in Richmond, Kentucky, on October 13, 2018. (Photo by Nicholas Kamm / AFP)        (Photo credit should read NICHOLAS KAMM/AFP via Getty Images)
NICHOLAS KAMM/AFP/AFP via Getty Images
US President Donald Trump speaks during a "Make America Great Again" rally at the Eastern Kentucky University, in Richmond, Kentucky, on October 13, 2018. (Photo by Nicholas Kamm / AFP) (Photo credit should read NICHOLAS KAMM/AFP via Getty Images)
Now playing
04:19
Haberman: This underscored for Trump that he's not president
WASHINGTON, DC - MARCH 29: Fox News host Tucker Carlson discusses 'Populism and the Right' during the National Review Institute's Ideas Summit at the Mandarin Oriental Hotel March 29, 2019 in Washington, DC. Carlson talked about a large variety of topics including dropping testosterone levels, increasing rates of suicide, unemployment, drug addiction and social hierarchy at the summit, which had the theme 'The Case for the American Experiment.'  (Photo by Chip Somodevilla/Getty Images)
Chip Somodevilla/Getty Images
WASHINGTON, DC - MARCH 29: Fox News host Tucker Carlson discusses 'Populism and the Right' during the National Review Institute's Ideas Summit at the Mandarin Oriental Hotel March 29, 2019 in Washington, DC. Carlson talked about a large variety of topics including dropping testosterone levels, increasing rates of suicide, unemployment, drug addiction and social hierarchy at the summit, which had the theme 'The Case for the American Experiment.' (Photo by Chip Somodevilla/Getty Images)
Now playing
02:48
Carlson promotes conspiracy that FBI planned Capitol riot
CNN
Now playing
02:55
Abrams says she is open to Manchin's voting rights legislation
CNN
Now playing
01:56
Toobin: Huge victory for Obamacare, but fight isn't over
Split Fanone Clyde
CNN/Pool
Split Fanone Clyde
Now playing
04:26
DC officer Fanone recalls interaction with GOP Rep.: He ran away 'like a coward'
President Joe Biden and Russian President Vladimir Putin, arrive to meet at the 'Villa la Grange', Wednesday, June 16, 2021, in Geneva, Switzerland.
Patrick Semansky/AP
President Joe Biden and Russian President Vladimir Putin, arrive to meet at the 'Villa la Grange', Wednesday, June 16, 2021, in Geneva, Switzerland.
Now playing
02:58
Biden and Putin hold first face-to-face meetings
Now playing
03:40
Arizona voting data taken to so-called 'lab' in remote Montana
President Joe Biden speaks to the news media following a news conference after meeting with Russian President Vladimir Putin, Wednesday, June 16, 2021, in Geneva, Switzerland.
Patrick Semansky/AP
President Joe Biden speaks to the news media following a news conference after meeting with Russian President Vladimir Putin, Wednesday, June 16, 2021, in Geneva, Switzerland.
Now playing
03:45
Biden apologizes for firing back at CNN's Kaitlan Collins after question
CNN
Now playing
11:01
Keilar and Berman: Vote shows GOP cares about police ... until they don't
weisselberg
JB Miller/Trump Organization
weisselberg
Now playing
01:43
NYT: Trump finance chief could face charges as early as this summer
Pro-Trump supporters storm the U.S. Capitol following a rally with President Donald Trump on January 6, 2021 in Washington, DC. Trump supporters gathered in the nation's capital today to protest the ratification of President-elect Joe Biden's Electoral College victory over President Trump in the 2020 election.
Samuel Corum/Getty Images
Pro-Trump supporters storm the U.S. Capitol following a rally with President Donald Trump on January 6, 2021 in Washington, DC. Trump supporters gathered in the nation's capital today to protest the ratification of President-elect Joe Biden's Electoral College victory over President Trump in the 2020 election.
Now playing
03:35
Avlon: There's a lot we still don't know about Jan. 6
Getty Images
Now playing
03:25
See top Trump DOJ official's two-word response to election probe request
US President Joe Biden gives a press conference after the NATO summit at the North Atlantic Treaty Organization (NATO) headquarters in Brussels, on June 14, 2021.
OLIVIER HOSLET/AFP/POOL/Getty Images
US President Joe Biden gives a press conference after the NATO summit at the North Atlantic Treaty Organization (NATO) headquarters in Brussels, on June 14, 2021.
Now playing
01:25
Biden calls on foreign leaders to protect against 'phony populism'
CNN
Now playing
01:39
Honig: Emails show Trump had his enablers
Senate TV
Now playing
05:54
McConnell dismisses Trump DOJ's secret seizure of data
Washington CNN —  

President Donald Trump on Sunday lashed out at a State Department employee who is set to testify publicly this week before lawmakers, the latest in a series of social media attacks made by the President against those cooperating in the House impeachment inquiry.

Jennifer Williams, an aide to Vice President Mike Pence and a career foreign service officer, is scheduled to appear before the House Intelligence Committee on Tuesday. In his Sunday tweet, Trump resurfaced an unfounded accusation he has raised against other officials who have testified in the probe, characterizing Williams as a Never Trumper and associating her with other “Never Trumpers.”

Tweeting a day after Williams’ earlier, closed-door testimony was released, Trump urged Williams to “read BOTH transcripts of the presidential calls.”

During a closed-door deposition earlier this month, Williams told lawmakers she was in the White House Situation Room listening to Trump’s July 25 phone call with Ukrainian President Volodymyr Zelensky in real time and reviewed a transcript of Trump’s April call prior to Pence’s own April call with Zelensky. Williams also listened to a second call between Pence and Zelensky, which took place on September 18 after the hold on security assistance was lifted.

Trump’s July 25 call is at the center of the impeachment inquiry, in which a whistleblower complaint alleges Trump asked for dirt on former Vice President Joe Biden, a 2020 presidential rival, and his son Hunter Biden. There is no evidence of wrongdoing by either Biden in Ukraine.

Williams testified that Trump’s request for specific investigations struck her as “unusual and inappropriate” and “shed some light on possible other motivations” for Trump’s decision to freeze security aid to Ukraine.

Pence’s office on Sunday declined to defend Williams after Trump’s Twitter attack.

“Jennifer is a State Department employee,” Pence’s press secretary Katie Waldman said in response to CNN’s request for comment.

Like many foreign policy advisers at the White House, Williams is a State Department employee detailed to Pence’s office.

Staffers in the vice president’s office have made a concerted effort to distance Pence from Williams, even before she sat down to testify. But sources explained to CNN that his office is selective about which career officials get detailed to their staff. His senior staff typically interviews them beforehand.

Keith Kellogg, the vice president’s national security adviser, was responsible for selecting Williams.

CNN has reached out to Williams and her attorney for comment, but has not received a response.

She is currently serving as a special adviser to the vice president for Europe and Russia. Current and former colleagues have praised Williams, with one White House official saying: “She is the most professional person in this building.”

Williams is just the latest government employee that Trump has accused without evidence of being a Never Trumper. He has also labeled Bill Taylor, the top US diplomat in Ukraine, and National Security Council official Lt. Col. Alexander Vindman as such.

CNN’s Greg Clary and Alex Marquardt contributed to this report.