Lieutenant Colonel Alexander Vindman, who serves as a director on the National Security Council (NSC), testified on Tuesday before the House committees overseeing the impeachment hearings about President Trump’s dealings with Ukrainian President Volodymyr Zelensky. In his prepared remarks, Vindman expressed concern that the president and members of his administration were risking US national security interests in the region.

Vindman twice approached the NSC’s lead counsel with concerns regarding the administration’s interactions with Ukraine. The first came after a July 10 meeting between National Security Advisor John Bolton and Oleksandr Danylyuk, Secretary of the National Security and Defense Council for Ukraine. Gordon Sondland, US Ambassador to the European Union, was also in attendance, and Vindman stated that during the meeting Sondland tried to talk about investigations that Ukraine should conduct in exchange for a meeting between Trump and Zelensky, when Sondland was cut short by Bolton. In a debriefing following that meeting, Sondland again brought up the need for Ukrainian investigations into former Vice President Joe Biden, Biden’s son Hunter, and Burisma Holdings, a Ukrainian energy company which Hunter Biden sat on the board of. Vindman objected that Sondland’s statements were inappropriate and had nothing to do with national security, and following the debriefing, he spoke to the NSC’s lead counsel.

Vindman also listened in on the July 25 call between Trump and Zelensky. He testified to the committee that the reconstructed transcript of the conversation released by the White House omitted statements by the president including an assertion that there were recordings of Vice President Biden discussing corruption in Ukraine. Vindman had submitted edits of the transcript that included the omitted material, but those edits were not fully incorporated into the released version. After the call, Vindman again spoke with the NSC’s counsel about his worries that President Trump’s demands for a Ukrainian investigation of the Bidens could be seen as a partisan attempt to harm a political rival, which would threaten bipartisan US support for Ukraine, a vital regional ally against Russian aggression.

Lieutenant Colonel Vindman could be called to testify again next month when public impeachment hearings are scheduled to begin.