Washington (CNN) Jennifer Williams, the special adviser to Vice President Pence on Europe and Russia who testified during the House impeachment inquiry last year, is leaving the Vice President's office two months ahead of her planned departure at the end of March, a White House official told CNN.

Williams is a detailee to Pence's staff from the State Department and is heading back to start another assignment as a deputy foreign policy adviser at US Central Command which oversees US troops in the Middle East and Central Asia..

She's had the assignment lined up since last fall, the official said, and she's leaving the Vice President's office early to do some training before heading to Tampa where CENTCOM is based. Her last day on Pence's staff is Monday.

The official did not dispute that Williams' role in the Ukraine saga influenced her early departure.

However, the vice president's office said Pence was still evaluating her request.

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