WASHINGTON – The White House's top expert on Ukraine twice notified superiors about concerns that the president and those working for him were linking foreign aid to Ukraine with investigations that would help President Donald Trump politically, a push that he said could undermine U.S. national security, according to an opening statement obtained by USA TODAY.

The testimony of Lt. Col. Alexander Vindman before the House Foreign Affairs, Intelligence and Oversight committees Tuesday will mark the first time lawmakers investigating the impeachment inquiry will hear from someone who listened to Trump's July 25 call with Ukrainian President Volodymyr Zelensky — the call at the center of the impeachment investigation that included a Trump's request that Ukraine investigate former Vice President Joe Biden.

"I was concerned by the call," Vindman wrote in the opening statement. "I did not think it was proper to demand that a foreign government investigate a U.S. citizen, and I was worried about the implications for the U.S. government’s support of Ukraine."

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In the six-page opening statement, Vindman, a key member of the National Security Council, outlined his dedicated service to the country, including his two decades as an Army officer, which included a tour in Iraq where he was wounded in an IED attack and awarded a Purple Heart. He says his family fled the Soviet Union and immigrated to New York City in 1979, giving him a deep appreciation of the American dream.

"I am a patriot," he says in the statement. "And it is my sacred duty and honor to advance and defend OUR country, irrespective of party or politics."

Vindman offered an overview of his role within the Trump administration in the testimony, including being tasked to attend Zelensky's inauguration in May, and details two specific events that he found concerning, "inappropriate" and led to him reporting the situation to the National Security Council's top lawyer.

The first was in July when a number of officials, including former National Security Advisor John Bolton, Ambassadors Kurt Volker and Gordon Sondland — two key witnesses that have testified to lawmakers — and Energy Secretary Rick Perry, who resigned earlier this month, met with Oleksandr Danylyuk, Ukraine's Secretary of National Security and Defense Council, according to the testimony.

The meeting in Washington was going well until the Ukrainians asked about a potential meeting between Trump and Zelensky, Vindman writes. That was when Sondland "started to speak about Ukraine delivering specific investigations in order to secure the meeting with the President."

Bolton then cut the meeting short, according to the testimony. Vindman wrote that after the meeting there was a debriefing where he confronted Sondland, saying "his statements were inappropriate, that the request to investigate Biden and his son had nothing to do with national security, and that such investigations were not something the NSC was going to get involved in or push."

It was after that meeting that Vindman reported his concerns to the National Security Council's chief lawyer.

Vindman said he reported a second concern after listening to Trump's July 25 call with Zelensky, where the president talked about military aid for the country, then asked about investigations into Biden and 2016 election.

He said Ukraine launching such investigations would push partisan politics into helping Ukraine fend off Russia, which would "undermine U.S. national security."

The New York Times first reported on Vindman's opening statement.