President Donald Trump's nominee to be ambassador to Russia faced questions about election interference and the ouster of the U.S. ambassador to Ukraine at his Senate confirmation hearing.

Deputy Secretary of State John Sullivan was the official who told Ambassador Marie Yovanovitch she was being recalled early from the Ukraine post. Her ouster is now central to the impeachment inquiry.

Sullivan said at his confirmation hearing Wednesday that he was told only that she had lost the confidence of the president. He said he was given no other explanation.

He told the committee that if confirmed he would be "relentless" in confronting Russia over its election interference and hostile moves against neighbors such as Georgia and Ukraine.

Sullivan is the second highest ranking official at the State Department.