UPDATE 1-Lt. Col. Vindman retiring from Army, alleges "bullying" by Trump

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By Phil Stewart and Idrees Ali

WASHINGTON, July 8 (Reuters) - Former White House aide Alexander Vindman, a key figure in the impeachment of President Donald Trump, said on Wednesday he was retiring from the Army after suffering what his attorney described as campaign of "bullying, intimidation, and retaliation" by Trump.

Vindman, an Army lieutenant colonel who had been due for a promotion, provided some of the most damaging testimony during an investigation by the U.S. House of Representatives into Trump's dealings with Ukraine.

Vindman confirmed to Reuters his decision to retire instead of becoming a colonel and wrote on Twitter that he and his family "look forward to the next chapter of our lives."

"After more than 21 years of military service, Lieutenant Colonel Alexander Vindman is retiring today after it has been made clear that his future within the institution he has dutifully served will forever be limited," according to a statement from his attorney.

Vindman, then the White House National Security Council's top Ukraine expert, testified that Trump's request for an investigation into former Vice President Joe Biden and his son Hunter during a July phone call with Ukraine President Volodymyr Zelenskiy was improper.

Vindman and his twin brother were escorted from the White House in February.

Trump has repeatedly complained about Vindman's testimony and called him insubordinate.

"Through a campaign of bullying, intimidation, and retaliation, the President of the United States attempted to force LTC Vindman to choose: Between adhering to the law or pleasing a President," the statement from Vindman's attorney said.

Defense Secretary Mark Esper said in November that Vindman should not fear retaliation over his testimony. At the time, Esper said he had reinforced the "no retaliation" message in a conversation with the secretary of the Army.

Last week, Democratic U.S. Senator Tammy Duckworth said she would put a hold on the confirmation of over 1,000 military promotions until Esper provided assurances on not blocking the promotion of Vindman. (Reporting by Phil Stewart and Idrees Ali Editing by Chizu Nomiyama and Jonathan Oatis)