– A White House adviser on Thursday corroborated key impeachment testimony from a senior U.S. diplomat who said last week that he was alarmed by efforts to pressure the Ukrainian government to investigate President Donald Trump's political rivals in exchange for nearly $400 million in military aid.

Tim Morrison, the top Russia and Europe adviser on Trump's National Security Council, told House investigators over eight hours of closed-door testimony that the "substance" of his conversations recalled by Bill Taylor, the acting ambassador to Ukraine, was "accurate," according to his prepared remarks and people familiar with Morrison's testimony.

In particular, Morrison verified that Trump's envoy to the European Union, Gordon Sondland, conveyed to a Ukrainian official that the military aid would be released if the country investigated an energy firm linked to the son of former Vice President Joe Biden. Morrison, who announced his resignation the night before his testimony, said he did not necessarily view the president's demands as improper or illegal, but rather problematic for U.S. policy in supporting an ally in the region.

His testimony is significant given his proximity to decision-making in the White House and his status as a Trump political appointee rather than one of several career officials who in recent weeks have offered critical testimonies of Trump's Ukraine policy. Democrats hope Morrison's testimony will take away an oft-cited Republican complaint that many of the accounts from U.S. officials describing a quid pro quo are secondhand.

Despite confirming Taylor's account about the pressure Trump's associates placed on Ukraine, Morrison did not come off during his closed-door testimony as outraged or particularly troubled by the effort, said people familiar with his deposition.

Yet Morrison twice reached out to National Security Council attorneys with apparent concerns about Trump's conversations pertaining to Ukraine policy, according to various witnesses' testimony. People familiar with his deposition said Morrison reported the July 25 phone call between Trump and Zelensky — as another White House official, Lt. Col. Alexander Vindman, had done.

Morrison told lawmakers that he notified the lawyers because he had specific concerns that a rough transcript of Trump's call with Zelensky could be leaked.