Two administration officials confirmed Trump's plans.
Nauert was formerly a co-host on morning cable news show "Fox & Friends" as well as a correspondent for CBS News.
President Donald Trump is expected to nominate State Department spokeswoman Heather Nauert to be his new ambassador to the United Nations, positioning a relatively inexperienced newcomer in one of the most high-profile positions in U.S. diplomacy, according to an administration official and a second source.
Nauert became the State Department spokesperson in April 2017 and, earlier this year, was named the acting undersecretary for public diplomacy and public affairs.
The 46-year-old former SC governor - one of the few women in the Trump cabinet - gave no reason for leaving, but dismissed speculation she was planning to run for president in 2020. Nauert would need to be confirmed by the Senate before taking up the role.
It was reported in November that Nauert had been offered the job, but it was not clear at the time whether she had accepted.More news: Start time, theme, iceberg rumours and more
According to multiple sources, the president will bring Heather Nauert from her current position as State Department spokeswoman to replace Haley at the United Nations.
Nauert did not respond to requests for comment.
She'll also take up the administration's efforts to defend Israel at the United Nations and counter what Haley called the organization's bias against the Jewish state. 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 U.S. Agency for Global Media that oversees government broadcast networks such as Voice of America.
The Illinois native would follow in the footsteps of Haley, a former governor of South Carolina; Samantha Power, a Pulitzer Prize victor; Susan Rice, a Rhodes Scholar; and former National Security Council and national security officials such as Madeleine Albright.
Israeli leaders nonetheless thanked her and feted the results as proof of wide support for Israel's position.
While Nauert struggled during the tenure of former Secretary of State Rex Tillerson - so ostracized from his inner circle that she considered quitting - she could now bring to the United Nations close ties to the White House and a good working relationship with Secretary of State Mike Pompeo. She met with Trump at the end of October, fueling speculation that she had emerged as the president's top choice for the role.