US President-elect Donald Trump has picked a former aide, Kash Patel, to lead the Federal Bureau of Investigation, an agency Patel has often criticised.

A former US Defence Department chief of staff in the first Trump administration, Patel has been a steadfast supporter of the incoming Republican president.

For Patel to take the job, the current FBI director Christopher Wray would need to resign or be fired - although Trump did not call on him to do so in his post.

Separately, Trump said he plans to nominate Chad Chronister, sheriff of Florida's Hillsborough County, as head of the Drug Enforcement Agency.

Patel and Chronister join Attorney General nominee Pam Bondi in filling out Trump's law enforcement picks.

All three choices will have to be confirmed by a majority vote in the US Senate.

Patel is Trump loyalist who shares the president-elect's suspicion of government institutions.

"Kash is a brilliant lawyer, investigator, and 'America First' fighter who has spent his career exposing corruption, defending justice, and protecting the American people," Trump posted on Truth Social, his social media platform, adding that Patel was "an advocate for truth, accountability, and the constitution".

But among Democrats and even some Trump allies, Kash could be seen as a divisive figure.

His past proposals have included “dramatically” limiting the FBI’s authority. In his memoir, Government Gangsters, Patel called for an eradication of what he called "government tyranny" within the FBI by firing "the top ranks”.

Trump's plan would have Patel replace current FBI director Christopher Wray, who Trump appointed in 2017 for the routine 10-year term.

But Wray fell out of favour with the president-elect when the FBI assisted with a federal probe into Trump's handling of classified records, a case that has since been dropped.

In a statement following Trump's announcement, the FBI said: "Every day, the men and women of the FBI continue to work to protect Americans from a growing array of threats.

"Director Wray's focus remains on the men and women of the FBI, the people we do the work with, and the people we do the work for."

Lawmakers react to Patel pick

In the hours after Trump picked Patel, legislators in both parties expressed their support of Wray, the current FBI director.

“I think the president picked a very good man to be the director of the FBI when he did that in his first term,” Republican Senator Mike Rounds of South Dakota said on ABC News on Sunday.

“When we meet with him behind closed doors, I've had no objections to the way that he's handled himself, and so I don't have any complaints about the way that he's done his job," he said.

National Security Advisor Jake Sullivan said on NBC's Meet the Press on Sunday that Wray was originally appointed by Trump, and that US President Joe Biden "didn't fire him".

“That’s how we approach things, and we would like to ensure that the FBI remains an independent institution insulated from politics,” he said.

Also on Meet the Press on Sunday, Democratic Congressman Chris Murphy went further, saying he was concerned that "Kash Patel is going to only care about protecting Republicans and not care about protecting every single member of the American population".

Meanwhile, some Republicans voiced their immediate enthusiasm for Patel.

Speaker of the House Mike Johnson was staunch in his support. "Kash Patel has extensive experience in national security and intelligence. He is an America First patriot who will bring much-needed change and transparency to the FBI," Johnson said.

Senator Bill Hagerty of Tennessee, said on Sunday he had encouraged Trump to select Patel.

“There are serious problems at the FBI," Hagerty said, also on Meet the Press. “The American public knows it. They expect to see sweeping change, and Kash Patel is just the type of person to do it.”

The son of Indian immigrants, Patel is a former defence lawyer and federal prosecutor who caught Trump’s eye after he became a senior counsel to the House of Representatives intelligence committee in 2017.

He was hired by Trump as a national security aide in 2019 and a year later was appointed chief of staff to the head of the Pentagon.

As well as his 2023 memoir, he has published two pro-Trump children’s books.

One of the titles, The Plot Against the King, features a villain, Hillary Queenton, trying to depose King Donald, who is aided by a wizard called Kash the Distinguished Discoverer.

Another villain is called Keeper Komey - a thinly veiled reference to former FBI Director James Comey - and his “spying slugs”, according to the book’s blurb.

Patel has often railed against the so-called “deep state”, which some Americans believe is an unelected bureaucratic machine that secretly runs the country for sinister purposes.

Patel has also excoriated the media, which he has called “the most powerful enemy the United States has ever seen”.

He is also on the board of Trump Media and Technology Group, which owns the incoming president’s social media platform Truth Social.

Patel reportedly has had a consulting contract with the company that paid him at least $120,000 a year.

Chronister also comes with a long background in law enforcement.

He has worked in law enforcement in Florida for 32 years, according to his official bio, and he has served as the top law enforcement officer in Hillsborough County, Florida, since 2017.

On social media, Trump praised Chronister's experience and reiterated his focus on drugs and the US border.

"As DEA Administrator, Chad will work with our great Attorney General, Pam Bondi, to secure the border, stop the flow of fentanyl, and other illegal drugs, across the southern border, and SAVE LIVES", Trump wrote.

Writing on social media, Chronister said it was "the honour of a lifetime to be nominated" by Trump.