WASHINGTON - President-elect Donald Trump shook up his transition team Friday as he plunged into the work of setting up his administration, elevating Vice President-elect Mike Pence to head the operations.

The move, one of the first key decisions as Trump pivots from campaigning to governing, amounted to a demotion for New Jersey's Gov. Christie, who had been running the Republican's transition planning for months.

On the heels of Trump's upset victory, his team has begun work on building a government, an undertaking that likely requires Trump to alter his hands-on management style and consider going outside his small, insular group of loyalists. He has been scrambling to identify people for top White House jobs and cabinet posts, a herculean task that must be well in hand by the time Trump is inaugurated on Jan. 20.

In a statement Friday, Trump said Pence would "build on the initial work" done by Christie. "Together, we will begin the urgent task of rebuilding this nation - specifically jobs, security and opportunity," Trump said.

Christie was a loyal adviser to Trump for much of the campaign, offered a key early endorsement, and came close to being the businessman's pick for running mate. But Trump ultimately went with Pence, the Indiana governor and a former congressman with Washington experience and deep ties to conservatives.

In addition to Christie's replacement, two of his confidants who were on the transition team - Rich Bagger, a former Christie chief of staff, and Bill Palatucci, a longtime adviser - will return to the private sector. Bagger and Palatucci will still be advisers to the team.

Christie was named the transition team's chairman in May. While he was passed over as Trump's running mate, his political prospects have been a topic of renewed speculation in the aftermath of Trump's election.

In an interview on NBC's Today on Thursday, Christie - whose term as governor ends in January 2018 - said he had not talked with Trump about a potential job in his administration.

"The president-elect was absolutely adamant about not discussing the transition before he was elected," Christie said. "And so he said to me back in May, '. . . You focus on getting this ready for me, and we'll talk on election night.' So we spoke on election night, but we didn't speak about me. We spoke about the transition."

Of whether he would want a certain White House job, "the bottom line is I have a job to do to help get the administration ready," Christie said.

In a statement Friday, Christie said he was "proud to have run the pre-election phase" of the transition team and thanked Trump for the "opportunity to continue to help lead." Christie will still be involved in the transition, joining a cluster of other steadfast Trump supporters serving as vice chairs: former House Speaker Newt Gingrich, retired neurosurgeon Ben Carson, retired Lt. Gen. Michael Flynn, former New York City Mayor Rudy Giuliani, and Alabama Sen. Jeff Sessions.

In addition, three of Trump's children - Donald Jr., Eric, and Ivanka - are on the transition executive committee, along with Jared Kushner, Ivanka Trump's husband. Kushner played a significant role in Trump's campaign and was spotted at the White House on Thursday meeting with President Obama's chief of staff.

The children's inclusion raises questions about the role the Trump family will play in the White House - as well as Trump's ability to sever ties between the administration and sprawling family business - after the celebrity businessman repeatedly said during the campaign that his adult children would not follow him to Washington and instead run the Trump Organization.

For Trump, who ran on a pledge to "drain the swamp" of Washington insiders, the team is strikingly heavy on those with long political resumes.

And another apparent contradiction emerged Friday as Trump, who repeatedly vowed to repeal the Affordable Care Act "on day one," said that he would be open to maintaining portions of Obama's signature legislative achievement.

Trump told the Wall Street Journal in an interview published Friday that, after speaking with Obama at the White House the day before, he was considering keeping the clause that allows children to stay on their parents' insurance policies. He has previously said he may keep the prohibition against insurers denying coverage because of patients' existing conditions.

He also said that he wants "a country that loves each other" but said he did not regret his incendiary rhetoric during the campaign.

"No. I won," Trump told the newspaper.

By appointing Pence, Trump became the first incoming president since at least Jimmy Carter to use his vice president-elect to run his transition team.

Trump and Christie grew apart through the last stretch of the campaign. The governor became increasingly frustrated that Trump wouldn't listen to his advice, particularly over the response to the release of a video in which the businessman is heard making predatory comments about women.

Christie is also facing calls for impeachment in New Jersey following the conviction of two former aides in the George Washington Bridge lane-closing trial. Christie has denied any knowledge of the lane closures until weeks or months after they occurred in September 2013.

The governor was notably absent from the steady stream of advisers entering Trump's eponymous skyscraper in New York for meetings Friday. Among the first decisions facing the president-elect is whom to choose as chief of staff, a top post that will set the tone for his White House and be a key conduit to Capitol Hill and cabinet agencies.

Trump is said to be considering Steve Bannon, his campaign chairman and a conservative media executive, and Republican National Committee Chairman Reince Priebus for the role. Neither has significant policy experience, though Priebus is well-liked in Washington and has ties with key lawmakers.

Kellyanne Conway, Trump's campaign manager, is also said to be in the mix for a senior job. Conway is a veteran Republican pollster who formed a strong rapport with the candidate after taking the helm of his campaign in the general election.

Giuliani, who emerged as Trump's frequent travel partner and close aide during the campaign's stretch run, is on the short list for several positions, including attorney general.

Staff writer Maddie Hanna contributed to this article.