Federal Bureau of Investigation Director Christopher Wray has said he will resign before President-elect Donald Trump, who has indicated he would fire him, takes office next month.

Wray announced at an internal FBI meeting on Wednesday that he had decided to step aside after weeks of consideration.

Trump has already nominated Kash Patel, who has called for "dramatically" limiting the FBI's authority, to lead the law-enforcement agency.

Wray, whom Trump nominated in 2017 to a 10-year term, has faced criticism during his tenure from Republicans due to the FBI's investigations into the former president after he left office.

Speaking at the FBI meeting on Wednesday, Wray said: "I've decided the right thing for the bureau is for me to serve until the end of the current administration in January and then step down."

"In my view, this is the best way to avoid dragging the bureau deeper into the fray, while reinforcing the values and principles that are so important to how we do our work," Wray added.

He received a standing ovation after his remarks, with some in the audience crying, an unnamed official told the Associated Press.

Trump appointed Wray to lead the FBI after firing his predecessor James Comey following the FBI's investigations into alleged contacts between the 2016 Trump campaign and Russia.

When appointing him, Trump said Wray - a Yale Law School graduate - was a man of "impeccable credentials".

But in recent years, Wray has fallen out of favour with the president-elect after the FBI assisted with a federal probe into Trump's handling of classified documents, a case that has since been dropped.

Trump said Wray's resignation was "a great day for America".

"It will end the Weaponization of what has become known as the United States Department of Injustice," he said on Truth Social. "We will now restore the rule of law for all Americans."

Following his election to a second term, Trump said his pick for FBI director would be Patel - a former aide who has been a steadfast supporter of the incoming Republican president.

On Wednesday, Patel said he was "looking forward to a smooth transition and I'll be ready to go on day one".

"Senators have been wonderful and I look forward to earning their trust and confidence through the advice and consent process, and restoring law and order and integrity to the FBI," he said.

Patel requires approval by the Senate before he can be appointed. In the meantime, FBI deputy director Paul Abbate, a veteran FBI agent, will run the bureau after Wray's departure, the BBC's US partner CBS News reported.

Patel has been a fierce critic of the FBI. In his memoir, Government Gangsters, Patel called for an eradication of "government tyranny" within the FBI by firing "the top ranks".

Patel's critics have expressed doubts that he is qualified to lead one of the world's top law enforcement agencies.

However, some Republican lawmakers have welcomed his nomination.

"Reform is badly needed at FBI," Senator Chuck Grassley of Iowa wrote on X following news of Wray's resignation, adding that the American people deserve transparency and accountability.

Wray has strongly denied he allowed a Democratic partisan agenda to run amok as FBI director, telling lawmakers a year ago at a House of Representatives hearing that he had been a lifelong Republican.

"The idea that I am biased against conservatives seems somewhat insane to me, given my own personal background," he said.