Ms Nauert, 48, was made state department spokeswoman in April 2017, her first government position.
The Trump administration will reportedly nominate State Department spokesperson Heather Nauert to replace Nikki Haley as ambassador to the United Nations next month.
Requests for comment to the state department and the White House were not immediately returned. 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.
Nuart was brought on to the administration after providing commentary on "Fox and Friends" on what appears to be Trump's favorite cable news network.
Haley unexpectedly announced her resignation in October and promised to serve in her role through the end of 2018.
She would be taking the position amid a roster of thorny global challenges, ranging from North Korea's nuclear program to Yemen's starvation and the growing divide between the U.S. and its closest allies over the Iran nuclear deal, climate change and other issues.
Still, with Trump, no staffing decision is final until he makes the formal announcement, since he has been known to change course in the past.
Back in October, Nauert, a former Fox News host, was believed to be a "leading contender" for the position, sources familiar with the selection process said at the time.
He pulled the United States out of the UN human rights body in September, citing bias towards Israel, and his administration has cut funding for the UN refugee agency and previous year proposed USA funding cuts for aid and diplomacy that could curb the work of the global body.
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. Trump is a regular viewer and one time guest of the show, and Nauert herself has developed a close relationship with Trump's daughter Ivanka.
Nauert, left, and White House press secretary Sarah Sanders. "What we've really discovered over the last two years is that even when you have a relatively mainstream, relatively collegial, relatively influential ambassador to the United Nations like Haley, that only buys you a limited degree of protection from a president like Trump".