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File photo taken on Dec. 1, 2017 shows U.S. Secretary of State Rex Tillerson turns to leave after a media opportunity with Libyan UN-backed Prime Minister Fayez al-Sarraj (not in the picture) at the State Department in Washington D.C., the United States. Rex Tillerson said on March 13, 2018 that he was delegating his official duties to Deputy State Secretary John Sullivan, and his tenure would terminate on March 31. (Xinhua/Yin Bogu)

WASHINGTON, March 13 (Xinhua) -- U.S. Secretary of State Rex Tillerson said on Tuesday he was delegating his official duties to Deputy State Secretary John Sullivan, and his tenure would terminate on March 31.

He said in a briefing packed with reporters that he would return to the private life, and it was most important to ensure "an orderly and smooth" transition of power to his successor Mike Pompeo, chief of Central Intelligence Agency (CIA).

In one of the biggest shakeup of his cabinet since assuming office early last year, Trump on Tuesday announced to nominate Pompeo to replace Tillerson.

Gina Haspel, Pompeo's deputy, will become the new director of the CIA as "the first woman so chosen," if the nominations could be confirmed by the Senate.