Washington (CNN) President Donald Trump announced on Friday that State Department spokeswoman Heather Nauert is his choice to succeed Nikki Haley as US ambassador to the United Nations, even as the White House moved to downgrade the job from a Cabinet-level position.

Speaking to reporters on the South Lawn of the White House, Trump said Nauert had done a "great job" at the State Department.

"She's very talented, very smart, very quick, and I think she's going to be respected by all," Trump said.

A senior administration official told CNN that Nauert attended Thursday night's Hanukkah party at the White House and Trump called her in to the Oval Office afterward.

United Nations Secretary General spokesman Stéphane Dujarric told CNN "we look forward to working with her [Nauert] when she assumes her functions."

A 'powerful voice'

"The UN Secretary-General had a good working relationship with Nikki Haley and looks forward to her successor," he said.

Nauert, a former Fox News host who arrived at the State Department in 2017, would be a relatively inexperienced newcomer in one of the most high-profile positions in US diplomacy. Her nomination sets the stage for a potentially tough Senate confirmation hearing, where Democrats will likely grill Nauert on her qualifications for the position.

In an administration rife with internal conflict and deeply distrustful of the UN, Nauert's nomination would place a less senior person at the international agency than Haley, who reportedly sparred with other administration officials.

Nauert got support from fellow members of the Trump administration, including Woody Johnson, the US ambassador to the UK, who said she would bring "a strong and powerful voice for American values of freedom and democracy around the world."

But the response from lawmakers was muted. Sen. Lindsey Graham, a South Carolina Republican close to Haley, his state's former governor, called Nauert "a fine and capable person. She was an effective spokeswoman for the Department of State and enjoys the confidence of Secretary Pompeo and President Trump."

Leaving aside the question of whether he has confidence in Nauert, Graham also glossed over how well she will perform in New York, saying, "I'm sure she will perform well at her hearing."

Nauert's appointment would realign power dynamics within the President's national security team. A senior White House official confirmed to CNN that the post will be downgraded from the Cabinet-level position that Haley had insisted on.

Secretary of State Mike Pompeo had told aides he wanted the post downgraded after Haley leaves, an official familiar with his remark has told CNN. Elevating Haley to a Cabinet member broke with the tradition of previous Republican administrations.

Less clout

National security adviser John Bolton has been said to want the role downgraded as well, according to people familiar with his thinking. A former UN ambassador himself, Bolton has taken an interest in some UN matters, such as the International Criminal Court.

The shift means Nauert, the latest in a long string of Fox News contributors or employees to enter Trump's administration, would wield less clout than her predecessor, both at the UN and within the administration, and as a result, would pose nowhere near the challenge to Bolton or Pompeo.

"If (Nauert) is kept outside the Cabinet, foreign diplomats will read that as a concrete signal ... that the post is being partly downgraded at the behest of Bolton and Pompeo. In a sense, it's a return to a norm," Richard Gowan, senior fellow at the UN University, New York, told CNN, adding that Haley was considered to be one of a few standout exceptions.

Qualifications questioned

But even if the position is downgraded, critics say Nauert's experience pales in comparison to others who have held the job.

"This is extraordinary. Especially in the footsteps of the former ambassadors: Madeleine Albright, Susan Rice," one senior diplomat told CNN about Nauert's nomination.

Peter Yeo, Senior VP of the UN Foundation, told CNN that "Nauert's selection doesn't fit the traditional mold for a US Ambassador to the UN."

"She has been a communicator more than a policy person, so she'll be quickly put to the test with the on-the-spot negotiations required at the UN. Although the position won't be Cabinet level, it remains unclear whether she'll be a separate center of power on UN issues in the Nikki Haley fashion," he said.

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Experience matters less to the President, an avid fan of Fox News, than Nauert's loyalty to the White House, the fact that she's a woman and her ability to be a polished proxy on television, according to sources familiar with his thinking.

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 UN close ties to the White House and a good working relationship with Pompeo.

During Pompeo's tenure, she rose to temporarily hold the position of acting under secretary for public diplomacy and public affairs.

A senior administration official said that Nauert has "extensive experience in this administration in foreign policy and in representing the President's goals."

In a statement Friday, Israel's ambassador to the UN, Danny Danon said he is confident Nauert will serve as a strong successor to Haley and believed her to be a strong supporter of Israel.

Despite Nauert's TV savvy, however, current and former colleagues wonder if she will be prepared or equipped to navigate the gritty behind-the-scenes work of UN negotiations.

She is also taking the position amid a roster of thorny global challenges, ranging from North Korea's nuclear program to Yemen's famine and the growing divide between the US and its closest allies over the Iran nuclear deal, climate change and other issues.