In a letter to Secretary of State Mike Pompeo dated January 4, Assistant Secretary for European and Eurasian Affairs A. Wess Mitchell said, "I feel that I have completed what I set out to do in taking this position."

Mitchell, who took on the role October 2017, said he was proud of the accomplishments made under his tenure but said "the time has come for (him) to spend more time with (his) young family."

The Washington Post was the first to report Mitchell's resignation, reports CNN.

In a tweet Tuesday, Pompeo commended Mitchell for "an outstanding job" in the role.

"I have valued his counsel and wisdom as he has led our European team in this administration. I wish him and his wife Elizabeth, who is also a committed public servant, much happiness with their two young children," Pompeo tweeted.

Deputy Spokesperson Robert Palladino also praised Mitchell's service.

"Assistant Secretary A. Wess Mitchell has been a valued and effective leader in @StateDept and good friend to our allies and partners in #Europe. We thank him for his service and wish him and his family well."

Palladino said that Elisabeth Millard, principal deputy assistant secretary, will serve as acting assistant secretary of state for the bureau.