(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.
An official working on the impeachment inquiry told CNN that Jennifer Williams was issued a subpoena Thursday morning for her deposition, "in light of an attempt by the White House to direct" her "not to appear."
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.
Justin Shur, Williams' attorney, told CNN in a statement Wednesday night that she would answer the committee's questions "if required to appear."
"Jennifer is a longtime dedicated State Department employee," Shur said in the statement. "If required to appear, she will answer the Committees' questions. We expect her testimony will largely reflect what is already in the public record."
Generally, the House has been sending subpoenas on the morning of their scheduled testimony.
Williams, a longtime State Department staffer, is detailed to Pence's office as special adviser on European and Russian affairs and was one of two Pence aides on the call. The other was Gen. Keith Kellogg, the vice president's national security adviser, who has not yet been called to testify.
Williams would be the first person on Pence's national security team to appear. She has knowledge of how much the vice president knew about the efforts by Trump and those around him to push Ukraine to launch investigations into former Vice President Joe Biden and his son, as well as 2016 election interference, a source familiar with her thinking told CNN.
Pence did not listen in, but a transcript of the call was put into his daily briefing binder, an administration source says.
He has repeatedly insisted that Trump did nothing wrong but Pence has not clarified how much he himself knew about efforts to pressure Ukraine and the parallel Ukraine policy that Trump's personal lawyer Rudy Giuliani and others were leading outside the normal diplomatic and official channels.
If she testifies, Williams would join a stream of other government officials who have given closed-door depositions in recent weeks as House investigators continue their impeachment inquiry stemming from a whistleblower complaint about Trump's July call with Zelensky.
A transcript of the conversation released by the White House shows Trump repeatedly pushed Zelensky to investigate Biden and his son, Hunter.
There is no evidence of wrongdoing by Joe or Hunter Biden.
This story has been updated with additional developments Thursday.
- Saudi shooter at Pensacola was taking aviation classes
- President Trump: ISIS leader Abu Bakr al-Baghdadi is dead
- Nashville cops nab 3rd escaped teen inmate
- Consider full evidence on impeachment
- Amazon will open a new office in New York City by 2021
- Ron Leibman, 'Norma Rae' and 'Friends' actor, dies at 82
- What we know about US military's program to train foreign troops
- Supreme Court blocks DOJ from restarting federal executions next week