Ms Nauert, who did not have a good relationship with Mr Tillerson and had considered leaving the department, told associates at the time she was taken aback by the promotion offer and recommended a colleague for the job.

But when White House officials told her they wanted her, she accepted.

That role gave her responsibilities far beyond the news conferences she held in the State Department briefing room. She oversaw public diplomacy in Washington and all of the roughly 275 overseas US embassies, consulates and other posts.

She was in charge of the Global Engagement Center that fights extremist messaging from the Islamic State group and others, and she has a seat on the US Agency for Global Media that oversees government broadcast networks such as Voice of America.