U.S. Department of State Spokesperson Heather Nauert speaks during a press conference in Washington, DC.

President Donald Trump has decided to name State Department spokeswoman Heather Nauert as the ambassador to the United Nations, a source familiar with his decision said on Thursday.

Trump will send a tweet on Friday morning about choosing Nauert to replace outgoing U.N. Ambassador Nikki Haley, who announced her resignation in October, Fox News reported, citing multiple sources.

Trump's decision was first reported by Bloomberg News. NBC News confirmed that report with multiple sources.

A representative of the State Department did not immediately respond to a request for comment.

Haley has held the post since the beginning of Trump's administration and said she would stay in the job through the end of the year.

Nauert, whose nomination would require Senate confirmation, is a former Fox News Channel correspondent and anchor. She does not have prior political or policy-making experience.

Nauert became the State Department spokeswoman in April 2017 and, earlier this year, was named the acting undersecretary for public diplomacy and public affairs.

ABC News reported in November that Nauert had been offered the job, but it was not clear at the time whether she had accepted.

—CNBC contributed to this report.