Donald Trump has named more conservative hardliners for key posts, with Alabama Senator Jeff Sessions nominated as attorney general.
Mr Sessions, a former prosecutor, was turned down for a federal judgeship in 1986 because of alleged racist remarks.
Congressman Mike Pompeo is nominated as CIA director and retired Lt Gen Michael Flynn made national security adviser.
Mr Trump's latest picks were praised on Twitter by David Duke, former leader of the white supremacist KKK group.
In a statement, Mr Trump called Mr Sessions a "world class legal mind".
"Jeff is greatly admired by legal scholars and virtually everyone who knows him," he added.
Mr Sessions said in a statement that he "enthusiastically" embraced President-elect Trump's vision for "one America and his commitment to equal justice under law".
"I look forward to fulfilling my duties with an unwavering dedication to fairness and impartiality," he said.
Mr Sessions, 69, and Gen Flynn, 57, have been close allies of Mr Trump since the early days of his campaign and share many of his views.
Mr Sessions opposes any path to citizenship for undocumented immigrants and was an enthusiastic backer of Mr Trump's pledge to build a wall on the border with Mexico.
In 1986, Mr Sessions was nominated by then-President Ronald Reagan for a federal judgeship, but was rejected because of allegations that he had made racist remarks. He strongly denied the claims.
Analysis by Anthony Zurcher, BBC News, Washington
The Trump administration is taking shape, and so far he is filling the top slots with men who are hardliners, close allies or both.
The president-elect has been making overtures towards portions of the party that opposed him, such as meeting with South Carolina Governor Nikki Haley on Thursday and scheduling a sit-down on Sunday with 2012 Republican nominee Mitt Romney - who earlier this year called him a con artist and a fraud.
Time will tell, however, whether those moves are legitimate efforts to diversify his coterie of advisers or just for show.
Jeff Sessions, the first major sitting politician to back Mr Trump, should ride the support of his Republican Senate colleagues to the attorney general spot despite the furore over alleged racist comments he made in the 1980s - ancient history at this point.
Retired Gen Michael Flynn's controversial rhetoric is much more recent but he is being advanced for a position that does not require Senate confirmation, so he will avoid a grilling from political opponents.
He had Mr Trump's ear during much of the campaign and now he will have it in the White House. So far, at least, the president-elect seems likely to get the team he wants.
Democratic senators voiced concern at Mr Sessions's nomination and said he would get a tough confirmation hearing.
"Given some of his past statements and his staunch opposition to immigration reform, I am very concerned about what he would do with the Civil Rights Division at the Department of Justice and want to hear what he has to say," said newly elected Democratic Senate leader Charles Schumer.
Gen Flynn, a vocal critic of the Obama administration since he was ousted as director of the Defence Intelligence Agency in 2014, agrees with Mr Trump on renegotiating the Iran nuclear deal, strengthening ties with Russia and intensifying the fight against Islamic extremists.
He once tweeted that fear of Muslims was "rational".
Kansas Republican Congressman Mr Pompeo, 52, originally backed Marco Rubio as the Republican candidate but supported Mr Trump after he won the nomination. He is a supporter of the conservative Tea Party movement.
Mr Pompeo has also been a fierce critic of President Barack Obama's nuclear deal with Iran, tweeting on Thursday: "I look forward to rolling back this disastrous deal with the world's largest state sponsor of terrorism."
Former Ku Klux Klan leader David Duke previously praised Mr Trump for his appointment of Stephen Bannon as chief White House adviser. But Mr Trump has poured scorn on the KKK and Mr Duke, describing him as "a bad person".