Trump announced Wednesday that he would announce a replacement for Haley by the end of the week.
Several news outlets, including CNN, are reporting that Trump will announce Nauert as his nominee Friday.
Haley officially announced in October she was leaving the post by the end of the year and had told the president earlier this year that she wanted to leave the job by the end of 2018.
During a joint appearance at the White House in early October, when Trump and Haley announced her departure, Haley told the president she is not running for president in 2020 and that she fully intends to campaign for him.
Trump confirmed last month that Nauert, who has very little foreign policy experience, was among those being considered to replace Haley.
At the time, the president said Nauert was "under very serious consideration," The Associated Press reported.
"She’s excellent. She’s been with us a long time," Trump said. "She’s been a supporter for a long time."
Nauert was hired at the State Department under former Secretary of State Rex Tillerson. She’s a former Fox News reporter, and she worked at ABC as a reporter before joining Fox.