National Security Council official Lt. Col. Alexander Vindman testified on Tuesday that President Donald Trumps ask of Ukrainian President Volodymyr Zelensky to open investigations into the 2016 election and former vice president Joe Biden was not a request, but an order.

There was a power disparity between the two leaders, Vindman said, due to Ukraines reliance on the United States for military and other aid.

When a senior asks you to do something even when its polite and pleasant its not to be taken as a request, its to be taken as an order, Vindman told the House Intelligence Committee as part of the ongoing impeachment inquiry into Trump.

After discussing the possibility of Zelensky visiting the White House in the July 25 call between the two leaders something the Ukrainian president badly wanted in order to boost his domestic standing Trump asked Zelensky to do us a favor though. He said Zelensky should announce investigations into a disproven conspiracy theory that Ukraine was involved in hacking the Democratic National Committee and into former vice president Joe Biden, a potential 2020 Trump opponent.

My impression was, in order to get the White House meeting, President Zelensky would have to agree to open these investigations, Vindman, who listened in on the July 25 call, said.

After the call concluded, without hesitation, I knew I had to report this to the White House counsel, Vindman said.

It was improper for the president to demand an investigation into a political opponent, especially a foreign power where theres at best dubious belief that this would be a completely impartial investigation, and that this would have significant implications if this became public knowledge ... it would undermine our Ukraine policy and it would undermine our national security, Vindman said.

At the time, Zelensky and other Ukrainian officials were not aware that U.S. military aid had been frozen on Trumps order and would be used as pressure to force Zelensky to announce these investigations. The Ukrainians would learn about this in early August, according to The New York Times .

Zelensky and his advisers believed they needed to announce these investigations to obtain the White House meeting and the release of the military aid. He planned on announcing the investigations in an interview with CNNs Fareed Zakaria in September.

The reporting of the whistleblower complaint about Trumps efforts to extort him to the House Intelligence Committee on Sept. 9, however, interrupted the whole plan. The White House freed the military aid two days later. And Zelensky did not announce the investigations.