WASHINGTON -- Lieutenant Colonel Alexander Vindman, a U.S. Army officer at the National Security Council, has testified that he believes a July 25 call between U.S. President Donald Trump and Ukraine's new president was 'improper' and that he reported his misgivings to the chain of command because he felt it 'would undermine our national security.'

Vindman, the White House National Security Council's top Ukraine expert, on November 19 told a Democratic-led House of Representatives impeachment inquiry into Trump and his dealings with Ukraine that 'it is improper for the president of the United States to demand a foreign government investigate a U.S. citizen and political opponent.'

Vindman was among those tasked with listening in on the call with Ukrainian President Volodymyr Zelenskiy, which has become the focus of the probe as lawmakers seek to learn whether Trump abused his office for personal and political gain by prodding Ukraine to investigate his political foes, including former Vice President Joe Biden, in exchange for releasing hundreds of millions of dollars worth of military aid.

Later in the questioning Vindman said he 'knew that I had to report [his concerns about the call] to the White House counsel. I had concerns and it was my duty to report my concerns to the proper people in the chain of command.'

Vindman, whose family fled the Soviet Union when he was three and a half years old, said that pressuring Kyiv to conduct an investigation into political rivals in return for military aid would 'undermine our Ukraine policy and it would undermine our national security.'

Vindman was testifying as the second week of public hearings in the impeachment inquiry got under way.

Jennifer Williams, a foreign-service aide to U.S. Vice President Mike Pence, sat next to the uniformed Vindman before the House Intelligence Committee, telling lawmakers that she found the July 25 call 'unusual' because it 'involved discussion of what appeared to be a domestic political matter.'

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