(Updates with details on Reeker's appearance, comments from lawmakers)
By David Morgan and Arshad Mohammed
WASHINGTON, Oct 26 (Reuters) - A senior U.S. diplomat on Saturday offered what Democrats characterized as corroborating testimony in the impeachment inquiry against President Donald Trump, although the witness was expected to tell lawmakers his knowledge of the events at hand was limited.
Philip Reeker, the acting assistant secretary of state for European and Eurasian affairs, met with the House of Representatives Foreign Affairs, Intelligence and Oversight committees behind closed doors at the U.S. Capitol.
Reeker was prepared to tell lawmakers he was unaware of whether U.S. security aid to Ukraine was withheld to pressure Kiev to launch investigations that could have helped Trump's 2020 re-election bid, according to a source familiar with the matter.
The Democratic-led panels are conducting an inquiry focusing on Trump's request that Ukrainian President Volodymyr Zelenskiy investigate former U.S. Vice President Joe Biden, a leading Democratic presidential candidate, and his son Hunter Biden, who had served on the board of a Ukrainian gas company.
U.S. election law prohibits candidates from accepting foreign help in an election.
As part of their probe, the lawmakers are examining whether Trump withheld $391 million in security assistance until Zelenskiy publicly committed to both an investigation of the Bidens and a debunked conspiracy theory that Ukraine - not Russia - meddled in the U.S. 2016 presidential election.
Democrats emerging from the session said Reeker's deposition corroborated previous testimony taken by the panels.
Representative Stephen Lynch told reporters that Reeker, whose portfolio includes Ukraine and Russia, was a "much richer reservoir of information than we originally expected."
But Reeker, according to the source who asked not to be identified, was largely out of the loop on policy toward Ukraine, leaving it to Kurt Volker, then the U.S. special representative for Ukraine negotiations, and others.
"There's no earth-shattering revelations. Nothing is new," Republican Representative Scott Perry said after several hours of testimony. "The accusations that are being leveled against the president aren't being corroborated in any of this witness testimony and today in my opinion is no different."
Reeker submitted to questioning in response to a congressional subpoena that was issued after the State Department attempted to block his testimony, according to an official working on the impeachment inquiry.
The testimony was the first since a federal judge on Friday rejected a claim by Trump and his Republican allies that the Democrats' impeachment inquiry process was illegitimate because the full House had not voted to authorize it.
House Speaker Nancy Pelosi on Sept. 24 launched the formal Trump probe under her broad powers as speaker.
The White House, citing the lack of an authorizing vote, had claimed the inquiry was "constitutionally invalid" and defied numerous congressional subpoenas for documents and testimony.
FOCUS ON UKRAINE
At the heart of the inquiry is a July 25 phone call in which Trump asked Zelenskiy to investigate the Bidens and a claim - debunked as a conspiracy theory - that a Democratic National Committee computer server was in Ukraine.
William Taylor, the top U.S. diplomat in Ukraine, testified on Tuesday that Trump made the withheld aid contingent on Zelenskiy announcing the requested investigations.
Reeker was unaware in the June-August period of the possibility Trump may have withheld the aid or a meeting to pressure Zelenskiy, the source said.
Trump denies wrongdoing and, backed by his fellow Republicans in Congress, insists he is being treated unfairly.
Reeker, 54, a career diplomat, is the latest in a growing list of current and former officials who have met with investigators.
Among the issues the committees were expected to explore with Reeker was Trump's abrupt dismissal in May of the ambassador to Ukraine, Marie Yovanovitch. According to emails given to congressional committees this month, Reeker sought to intervene when Trump supporters accused Yovanovitch of being disloyal to the president.
Reeker sought a stronger State Department defense of Yovanovitch under U.S. Secretary of State Mike Pompeo's name, according to the source familiar with the matter, but this appeared to have been stymied "from the top," though it was not clear if Pompeo himself had objected.
The committees have scheduled several depositions for next week, all behind closed doors.
Charles Kupperman, a former deputy national security adviser to Trump, who was called to appear on Monday, has asked a court whether he should to comply with a congressional subpoena or honor the administration's instruction not to testify.
On Tuesday, lawmakers expect to hear from Alexander Vindman, the White House National Security Council's top Ukraine expert.
Kathryn Wheelbarger, acting assistant secretary of defense for international security, is scheduled to appear on Wednesday, and Tim Morrison, a top White House adviser on Russia and Europe, is scheduled for Thursday. (Reporting by David Morgan and Arshad Mohammed; Additional reporting by Patricia Zengerle; Writing by Patricia Zengerle and Richard Cowan; Editing by Leslie Adler, Chizu Nomiyama and Daniel Wallis)
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