US president Donald Trump is expected to announce he will nominate State Department spokeswoman Heather Nauert to be the next US ambassador to the United Nations, officials said.

Two administration officials confirmed Mr Trump’s plans.

A Republican congressional aide said the president was expected to announce his decision by tweet on Friday morning.

Mr Trump has previously said Ms Nauert was under serious consideration to replace Nikki Haley, who announced in October that she would step down at the end of this year.

If Ms Nauert is confirmed by the Senate, she would be a leading administration voice on Trump’s foreign policy.

Mr Trump told reporters last month that Ms Nauert was “excellent,” adding, “She’s been a supporter for a long time.”

Nikki Haley Award
Nikki Haley announced in October that she would step down at the end of this year (Seth Wenig/AP)

Still, with Mr Trump, no staffing decision is final until he makes the formal announcement, since he has been known to change course in the past.

Ms Nauert did not respond to requests for comment.

She was a reporter for Fox News Channel before she became State Department spokeswoman under former secretary Rex Tillerson.

Plucked from Fox by the White House to serve as State Department spokeswoman, Ms Nauert catapulted into the upper echelons of the agency’s hierarchy when Mr Tillerson was fired in March and replaced with Mike Pompeo.

Ms Nauert was then appointed acting undersecretary of state for public diplomacy and public affairs and was for a time the highest-ranking woman and fourth highest-ranking official in the building.

Trump Hanukkah
Donald Trump called Heather Nauert ‘excellent’ last month (Jacquelyn Martin/AP)

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.

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 Centre 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.

Just 18 months ago, she was not in government.

Ms Nauert was a breaking news anchor on Mr Trump’s favourite television show, Fox & Friends, when she was tapped to be the face and voice of the administration’s foreign policy.

With a master’s degree from Columbia University’s Graduate School of Journalism, she had come to Fox from ABC News, where she was a general assignment reporter.

White House press secretary Sarah Huckabee Sanders described Ms Nauert in March as “a team player” and “a strong asset for the administration”.