William Taylor is expected to leave his role as U.S. ambassador to Ukraine on Jan. 1, just over a month after testifying in the House impeachment hearings.

The ambassador told NBC News that he would be leaving his position at the beginning of the new year. Deputy Chief of Mission to Ukraine Kristina Kvien will take over the position as acting ambassador, and Taylor is expected to leave Ukraine on Jan. 2.

Taylor, 72, was called in by House Democrats to provide context related to President Trump’s phone call with Ukrainian President Zelensky. Democrats filed two articles of impeachment following testimony from Taylor and others alleging that Trump abused his power and obstructed justice.

At the time, Taylor called Trump’s request for an investigation into Biden in return for military aid “crazy” but offered a much more reserved testimony before the House Intelligence Committee. He refused to say whether he witnessed a quid pro quo and offered some positive words about Trump’s effort to help Ukraine by providing them with lethal weapons .

Taylor and Trump had a rocky relationship. The president called Taylor a Never Trumper prior to his congressional testimony.

Trump will be responsible for choosing a permanent replacement for Taylor. His nominee will be subject to Senate confirmation.