CNN image(CNN) - An aide to Vice President Mike Pence -- who was concerned about the July 25 call between President Donald Trump and the Ukranian President -- is testifying behind closed doors Thursday, the latest deposition for the Democratic-led House impeachment inquiry.
Williams was on the July 25 call between Trump and Ukraine President Volodymr Zelensky, and she was concerned about what she heard on the call but there is no indication Williams raised her concerns to her superiors, according to the source.
The other was Gen. Keith Kellogg, the vice president's national security adviser, who has not yet been called to testify.
Pence did not listen in, but a transcript of the call was put into his daily briefing binder, an administration source says.
A transcript of the conversation released by the White House shows Trump repeatedly pushed Zelensky to investigate Biden and his son, Hunter.