Washington, Nov 20 (IANS): The White House on Wednesday slammed top Ukraine official Lt Col Alexander Vindman after he testified to an impeachment hearing that a phone call made by the US President Donald Trump to his Ukranian counterpart Volodymyr Zelensky was "improper" and had left him in "shock".

Lt Col Alexander Vindman told US Congress on Tuesday that Trump made "inappropriate" political demands during the call, BBC reported, citing US media reports.

"I couldn't believe what I was hearing," Lt Col Vindman said.

The hearings are investigating whether Trump abused his presidential power.

Lt Col Vindman, a decorated Iraq war veteran who serves in a senior role on the US National Security Council (NSC) testified before the House in his Army uniform.

The White House official Twitter account was used throughout the hearing to attack Vindman.

"Vindman made it clear that he gave information about President Trump's phone call with President Zelensky to an unnamed individual. Schiff shut down questioning about the unnamed individual to "protect the whistleblower". But neither one knows who the whistleblower is?," the White House tweeted.

In another tweet, the White House said, "...we have Vindman, who never met or spoke to POTUS, testifying of alarming 'demands' in the 7/25 call."