Nauert also now serves as the acting Under Secretary for Public Diplomacy and Public Affairs at the State Department.
Ms Nauert worked for Fox News from 1998 to 2005 and, after two years away during which she worked for ABC, she returned to Fox in 2007, later becoming a presenter for Fox & Friends.
Numerous reports in the USA media - the first of which appeared in Bloomberg news - said Nauert would be nominated Friday, citing sources close to the matter.
Heather Nauert, who earlier this year had been considered a possible successor to White House spokeswoman, Sarah Sanders, gained experience on diplomacy by working at the State Department, but she lacks the political and policy credentials of Ms Haley, who is a former governor of SC.
The announcement is expected to come on Friday, two officials say.
China Stops Work on Gene-Edited Babies
Other concerns have focused on the CCR5 gene, which scientists at the conference said is crucial to the human immune system. The conference was rocked by the Chinese researcher's claim to have helped make the world's first gene-edited babies.
If confirmed, Ms Nauert's appointment could prove controversial given her apparent lack of foreign policy experience. Nauert would need to be confirmed by the Senate before taking up the role.
"If Nauert is nominated and approved, people will be interested to see whether she's willing and able to do the diplomatic toil or whether she will see this as an extension of the spokesman position and focus more on presentation of United States position before the Security Council", said Gowan. Haley argued for a Cabinet-level post after, she said, initially being considered for the secretary of state job.
Trump is reportedly weighing other staff changes before the end of the year, including replacing White House Chief of Staff John Kelly.
"To be blunt, it's seen as a win simply that it's not Grenell", who is known to share Bolton's "pugilistic approach" to worldwide institution, Gowan said.
In the end, though, it might not matter who is ambassador, Gowan said.
Haley has been the U.S. ambassador to the United Nations for the entirety of Trump's presidency.