Impeachment inquiry: Who is testifying before Congress this week?

At least four people are expected to testify before U.S. House committees this week in the impeachment inquiry against President Donald Trump.

The former ambassador to Ukraine, a state department counselor, the U.S. ambassador to the European Union and a deputy secretary of State are all scheduled to appear in private before committees assigned to lead the impeachment inquiry against Trump.

The inquiry, which was announced by House Speaker Nancy Pelosi on Sept. 24, was launched after a whistleblower contacted members of Congress with concerns about a phone call Trump made in July to the president of Ukraine.

The phone call, according to Trump critics, had the president leveraging his power to hold $400 million in aid to Ukraine in exchange for information on former Vice President Joe Biden and his son Hunter Biden. Trump says the call congratulating Volodymyr Zelenskiy on becoming president of Ukraine was “perfect” and has been misinterpreted.

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Trump claims that Hunter Biden profited from an affiliation with a Ukrainian gas company and that Joe Biden had a prosecutor who was looking into the operations of the gas company fired to protect his son. Neither Biden has been officially accused of wrongdoing.

Scheduled to testify before House committees this week are:

George Kent, deputy secretary of state. Kent is scheduled to testify on Monday. Kent oversees policy toward Ukraine in his State Department job. From 2015 to 2018, Kent was deputy chief of mission at the U.S. Embassy in Kyiv. Part of his job was to form anti-corruption policy in the region before 2015.

Gordon Sondland, the U.S. ambassador to the European Union. Sondland is expected to testify on Tuesday. According to the whistleblower's complaint, Sondland, along with Volker, offered advice to the "Ukrainian leadership about how to "navigate" the demands that the President had made of Mr. Zelensky." Sondland and Volker also met with Giuliani, the whistleblower complaint said, to "attempt to contain the damage to U.S. national security" that Giuliani's efforts to find information on Biden was having.

Ulrich Brechbuhl, a State Department counselor. Brechbuhl is also scheduled to testify on Tuesday. According to the whistleblower's complaint, Brechbuhl was on the July 25 phone call.

Masha Yovanovitch, former ambassador to Ukraine. Yovanovitch, who was recalled from her post after her loyalty to Trump was questioned by some of her supporters, is set to testify on Friday.