Sanders told reporters the timeline for Hicks' departure was unclear. She said her departure was not related to her testimony to a congressional committee on Tuesday about an investigation into Russian meddling in the 2016 US election.
She is expected to leave in the next few weeks.
Hicks, 29, was caught up in a controversy surrounding former White House staff secretary Rob Porter, whom she had been dating. She worked to defend him when charges of domestic abuse against his two former wives emerged. Porter was ultimately forced to resign.
She was one of the first people hired by then-businessman Trump when he began his campaign for the presidency, and is one of his most trusted advisers. Aides said she had approached the president and told him she wanted to leave so she could start exploring opportunities outside of the White House.
"Hope is outstanding and has done great work for the last three years. She is as smart and thoughtful as they come, a truly great person," Trump said in a statement released by the White House. "I will miss having her by my side but when she approached me about pursuing other opportunities, I totally understood. I am sure we will work together again in the future."
White House Chief of Staff John Kelly said in a statement of Hicks: "To say that she will be missed, is an understatement."
Hicks took over as communications director in September after the short, difficult tenure of Anthony Scaramucci, who was fired. She is credited behind the scenes for stabilizing the communications operation.
Hicks said in a statement: "There are no words to adequately express my gratitude to President Trump. I wish the President and his administration the very best as he continues to lead our country."
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
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