Lt. Col. Alexander Vindman, director for European Affairs at the National Security Council, arrives for a closed-door hearing on Capitol Hill to testify as part of the U.S. House of Representatives impeachment inquiry into U.S. President Trump, in Washington, U.S., November 7, 2019. REUTERS/Tom Brenner

WASHINGTON (Reuters) - A U.S. national-security adviser told lawmakers leading an impeachment investigation into President Donald Trump there was “no ambiguity” that a U.S. ambassador told Ukrainian officials to investigate former Vice President Joe Biden and his son, according to testimony released on Friday.

“There was no ambiguity, I guess, in my mind. He was calling for something, calling for an investigation that didn’t exist into the Bidens,” Lt. Col. Alexander Vindman said, referring to Gordon Sondland, the U.S. ambassador to the European Union.

Vindman, who serves on the White House National Security Council, said the U.S.-Ukraine relationship “is damaged” and “will continue to be damaged and undercut.”