Washington (CNN) Lt. Col. Alexander Vindman, the National Security Council official testifying publicly as part of the House impeachment inquiry into President Donald Trump, has reached out to the US Army about the security of his family as he comes under repeated attack by Trump and his allies.

The Army has had conversations with Vindman about the security of his family, a US defense official told CNN. These conversations were initiated at the request of the Vindmans, the source said. As of now, the Army does not believe there is an imminent security threat against the decorated veteran, the defense official said.

Vindman testified before congressional lawmakers on Tuesday, telling them that Trump's push for Ukraine to investigate former Vice President Joe Biden on a July call was "inappropriate," and he knew "without hesitation" that he had to report it. There is no evidence of wrongdoing by Biden in Ukraine.

"It is improper for the President of the United States to demand a foreign government investigate a US citizen and political opponent," Vindman said in his opening remarks on the third day of public impeachment hearings.

'My family's safety'

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