Philip Reeker, a senior State Department official, appeared Saturday on Capitol Hill to testify behind closed doors to three House committees conducting an impeachment inquiry against President Donald Trump.

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Reeker, the acting assistant secretary in charge of European and Eurasian affairs, oversaw officials who dealt directly with Trump's personal lawyer, Rudy Giuliani, on Ukraine matters, The New York Times reported.

While no bombshell news is expected, Reeker is may provide information about an alleged effort to pressure Ukrainian officials to investigate former vice president Joe Biden and his son, Hunter Biden, according to The Washington Post.

It is not clear how much Reeker knew about the effort, in which Ukraine's president, Volodymyr Zelensky, allegedly was pressured to publicly announce an investigation of the Biden family before President Trump would agree to meet Zelensky or release $391 million in military aid.

Reeker is a career diplomat with a reputation for being apolitical and hard-working, the newspaper reported. He has served as a diplomat in Iraq, Germany, Italy, Hungary and Macedonia, the Times reported.

Reeker joined the State Department in 1992, according to the Post.