(CNN) Rep. Mark Meadows resigned from Congress on Monday as he prepares to officially become White House chief of staff.

"Serving the people of North Carolina's eleventh congressional district for these last seven years has been the honor of my life," he wrote in a letter to House Speaker Nancy Pelosi. "I will forever be grateful for the opportunity."

He wrote that his resignation was effective as of 5 p.m. ET.

Meadows has been at President Donald Trump's side for the last several weeks as part of a transition period. He will officially have his first day as White House chief of staff on Tuesday, a Meadows aide told CNN.

Meadows will be Trump's fourth chief of staff, replacing Mick Mulvaney, another former congressman, in the position.

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