National Security Council Ukraine expert Lieutenant Colonel Alexander Vindman leaves the Longworth building after testifying during the House Intelligence Committee hearing, into President Donald Trump's alleged efforts to tie US aid for Ukraine to investigations of his political opponents.

A key witness in the impeachment investigation into US President Donald Trump‘s alleged arms-for-investigations Ukraine scandal testified Tuesday that a senior Kiev official offered him the job of defense minister.

Lieutenant Colonel Alexander Vindman, a Ukraine expert on the White House National Security Council, told a congressional impeachment hearing he did not take the offer seriously.

Republicans brought up the offer from Oleksandr Danylyuk, the former secretary of Ukraine’s National Security and Defense Council, in an apparent bid to discredit Vindman’s damning testimony against Trump.

Vindman said Danylyuk dangled the post three times during a meeting in Kiev on the occasion of Ukraine President Volodymyr Zelensky’s April inauguration.

“But every single time, I dismissed it,” Vindman told the House Intelligence Committee, adding that he reported the offer to his superiors in the US government.

“I think it would be a great honor and frankly I’m aware of service members that have left service to help nurture the developing democracies in that part of the world,” he said.

He stressed however: “I’m an American — I came here when I was a toddler — and I immediately dismissed these offers.”

Democrats are investigating allegations that Trump abused his office by bullying Ukraine into launching investigations that would benefit the president politically while the White House was withholding nearly $400 million in vital military aid.

Vindman said Trump’s request for political favors, including to investigate Democrat Joe Biden, in a July 25 phone call with Zelensky was “inappropriate” and “improper”.

While Democrats have held up Vindman’s testimony as evidence of Trump’s abuse of his powers, Republicans have sought to paint the decorated veteran as disloyal to Trump and even, possibly, to the United States.

Kiev-born Vindman called the job offer “rather comical.”

“It is pretty funny for a lieutenant colonel in the United States army, which really is not that senior, to be offered that illustrious a position,” he said.

He said he flatly turned it down, and his superiors never expressed concern after he reported it.

“Frankly, if they were concerned about me being able to continue my duties, they would have brought that to my attention,” he said.