CIA director John Brennan on Sunday had a stern parting message for Trump days before he assumes the U.S. presidency, cautioning him against loosening sanctions on Russia and warning him to watch what he says.

Brennan rebuked the president-elect for comparing U.S. intelligence practices to Nazi Germany in comments that laid bare the friction between Trump and the intelligence community he has criticized and is on the verge of commanding.

In an interview with Fox News Sunday, Brennan questioned the message sent to the world if the president-elect broadcasts that he does not have confidence in the United States' own intelligence agencies.

"What I do find outrageous is equating intelligence community with Nazi Germany," Brennan said. "I do take great umbrage at that."

His comments followed a tumultuous week of finger-pointing between Trump and intelligence agency leaders over the unsubstantiated report of compromising information Moscow had collected on Trump.

Trump accused the intelligence community of leaking the compromising information, which its leaders denied. They said it was their responsibility to inform the president-elect that the allegations were being circulated.

USA-CIA/BRENNAN

Central Intelligence Agency (CIA) director John Brennan issued a stern warning to the president-elect on Sunday, saying he needs to watch what he says about Russia and be more aware of what he posts on Twitter. (Gary Cameron/Reuters)

Later on Sunday, Trump took to Twitter to berate Brennan and wrote, "Was this the leaker of Fake News?" In a separate posting, Trump scolded "those intelligence chiefs" for presenting the dossier as part of their briefing. "When people make mistakes, they should APOLOGIZE," he wrote.

Brennan also sounded an alarm on the topic of U.S. relations with Russia, something Trump has vowed to improve as he fights criticism that he is too eager to make an ally of Russian President Vladimir Putin.

Trump does not yet have a full understanding of Russia's actions, Brennan said, noting its seizure of Crimea from Ukraine, its support for President Bashar al-Assad in Syria's civil war and Moscow's activities in the cyber realm.

"Mr. Trump has to understand that absolving Russia of various actions it has taken in the past number of years is a road that he I think needs to be very, very careful about moving down," he told Fox.

'I think nuclear weapons should be way down'

Also Sunday, a wide-ranging interview Trump gave to the Times of London was published. The president-elect discussed topics such as sanctions against Russia, reducing nuclear arms, NATO and his son-in-law's role in foreign affairs.

Trump told the Times that he would propose offering to end sanctions imposed on Russia for its annexation of Crimea in return for a nuclear arms reduction deal.

Trump also said he wanted nuclear weapons arsenals of the world's two biggest nuclear powers —the United States and Russia — to be "reduced very substantially."

"They have sanctions on Russia — let's see if we can make some good deals with Russia. For one thing, I think nuclear weapons should be way down and reduced very substantially, that's part of it," Trump was quoted by the newspaper.

Parliamentarians in Russia gave a mixed reaction to Trump's proposal.

Konstantin Kosachev, head of the upper house of parliament's international affairs committee, was cited by the RIA Novosti news agency as saying getting the sanctions annulled was not a goal in itself and not worth making security concessions for.

"We consider them [the sanctions] a stupid legacy of the outgoing White House team that need to be consigned to history along with them," said Kosachev.

But another Russian senator, Oleg Morozov, was quoted by the same agency as saying that Moscow would be ready to discuss the issue of nuclear cuts, something he said Russia itself favoured.

Repeats NATO criticisms

Trump in the interview also criticized Russia for its intervention in the Syrian civil war, describing it as "a very bad thing" that had led to a "terrible humanitarian situation," The Times said.

He also used the interview to try and explain his criticism of the NATO agreement.

"I took such heat, when I said NATO was obsolete," Trump told the newspaper in an interview. "It's obsolete because it wasn't taking care of terror. I took a lot of heat for two days. And then they started saying Trump is right."

Trump added that many NATO members were not paying their fair share for U.S. protection.

"A lot of these countries aren't paying what they're supposed to be paying, which I think is very unfair to the United States," Trump said. "With that being said, NATO is very important to me. There's five countries that are paying what they're supposed to. Five. It's not much."

Trump told The Times that he would appoint Jared Kushner, his son-in-law, to broker a Middle East peace deal and urged Britain to veto any new UN Security Council resolution critical of Israel.

With files from The Associated Press