Lt. Col. Alexander Vindman rebuffed Republican attacks on his loyalty during impeachment proceedings Tuesday, calling Ukraines offer of a post in its government comical.

The exchange came as Republican staff lawyer Steve Castor pushed hard on the GOP line first propagated by Fox News that Vindman, the director for European affairs at the National Security Council, might have dual loyalty to both the U.S. and Ukraine , where he was born.

Vindman attended the inauguration of Ukrainian President Volodymyr Zelensky , during which Ukrainian national security council secretary Oleksandr Danyliuk repeatedly offered him the post of defense minister, Castor revealed Tuesday.

Vindman said he dismissed the offer every single time, and reported it to the appropriate officials, including counterintelligence officers, once he returned to the U.S.

Im an American, he said. I came here when I was a toddler. I immediately dismissed these offers. I did not entertain them.

Castor nevertheless kept pushing the idea and implied that, had Danyliuk made the offer in Ukrainian, it would represent an attempt to somehow sway Vindman.

Vindman responded that the offer was made in English, and made in the presence of two staff officers from the American Embassy in Ukraine.

The whole notion is rather comical, Vindman said. I did not leave the door open at all. It is pretty funny for a lieutenant colonel of the U.S. Army which really isnt that senior to be offered that illustrious a position.

As a reminder, Vindman is a Harvard-educated officer who served multiple overseas tours in South Korea, Germany and Iraq, where he was injured by a roadside bomb, for which he received a Purple Heart. His father immigrated to the U.S. from the Soviet Union 40 years ago in search of a better life for our family, Vindman said Tuesday .

Vindman was testifying Tuesday alongside Jennifer Williams, a top special adviser to Vice President Mike Pence for Europe and Russia affairs. Both were on the President Donald Trump s July 25 call with Zelensky, which is at the center of the impeachment inquiry.