Fiona Hill, President Trump's former top Russia and Europe adviser, was reportedly quite concerned that Gordon Sondland, the U.S. ambassador to the European Union, would accidentally divulge national security secrets while on the job, two people familiar with her private congressional testimony told The New York Times.

Hill reportedly testified on Monday that Sondland was so unprepared for his job that she considered him a national security threat, though she apparently did not accuse him of intentionally putting the country at risk. Instead, she reportedly likened him to someone driving a car without guardrails or a GPS.

The actions that are said to have concerned Hill include Sondland's use of a personal cell phone for diplomatic business and his penchant for inviting foreign officials to pop by the White House whenever they felt like it, which once reportedly resulted in Romanian officials arriving at the White House without an appointment. Sondland, Hill reportedly testified, would also provide the cell phone numbers for other American officials to foreigners.

Hill's concerns were likely enhanced by the fact that she feared Sondland was replacing Washington's previous ambassador to Ukraine, Marie Yovanovitch, as part of the Trump administration's effort to pressure Kyiv into investigating former Vice President Joe Biden and his son, Hunter, among other Democratic figures. Sondland is expected to testify before impeachment investigators Thursday, despite the White House directing him not to cooperate. Read more at The New York Times. Tim O'Donnell