CIA Director John Brennan on Sunday offered a stern parting message for Donald Trump days before the Republican U.S. president-elect takes office, cautioning him against loosening sanctions on Russia and warning him to watch what he says.

Brennan rebuked Trump for comparing U.S. intelligence agencies to Nazi Germany in comments by the outgoing CIA chief that reflected the extraordinary friction between the incoming president and the 17 intelligence agencies he will begin to command once he takes office on Friday.

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 the intelligence community with Nazi Germany. I do take great umbrage at that, and there is no basis for Mr. Trump to point fingers at the intelligence community for leaking information that was already available publicly," Brennan said.

Brennan's criticism followed a tumultuous week of finger-pointing between Trump and intelligence agency leaders over an unsubstantiated report that Russia had collected compromising information about Trump.

The unverified dossier was summarized in a U.S. intelligence report presented to Trump and outgoing President Barack Obama this month that concluded Russia tried to sway the outcome of the Nov. 8 election in Trump's favor by hacking and other means. The report did not make an assessment on whether Russia's attempts affected the election's outcome.

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

Later on Sunday, Trump took to Twitter again to berate "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 U.S. relations with Russia. Trump has vowed to improve relations with Moscow even as he faces 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 aggressive 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," Brennan said.

In an interview with the Wall Street Journal published on Friday, Trump suggested he might do away with sanctions imposed by the Obama administration on Russia in late December in response to the cyber attacks if Moscow proves helpful in battling terrorists and reaching other U.S. goals.

PROFOUND IMPLICATIONS

Brennan also said Trump needs to be mindful about his off-the-cuff remarks once he assumes the presidency, alluding to Trump's penchant for making broad pronouncements on Twitter.

"Spontaneity is not something that protects national security interests," Brennan said. "So therefore when he speaks or when he reacts, just make sure he understands that the implications and impact on the United States could be profound."

"It's more than just about Mr. Trump. It's about the United States of America," Brennan said.

Trump has picked Mike Pompeo, a Republican member of the House of Representatives and a former U.S. Army officer, to replace Brennan.

Trump's comments about Putin and his reluctance to assign blame to Moscow for the hacking of Democratic political groups has opened him up to criticism that he will be too soft on Russia.

For months, Trump had publicly expressed doubt about U.S. intelligence conclusions on the cyber attacks before acknowledging at a news conference on Wednesday that he thought Russia was behind the hacking.

Vice President-elect Mike Pence told "Fox News Sunday,""What the president-elect is determined to do is to explore the possibility of better relations."

Pence did not say whether Trump would undo some of the sanctions and diplomatic expulsions Obama had slapped on Moscow.

Pence confirmed that Trump's incoming national security adviser, Michael Flynn, held conversations with the Russian ambassador to Washington around the time the sanctions were imposed, but said the talks "were not in any way related to the new U.S. sanctions against Russia or the expulsion of diplomats."

However, Pence denied that Trump's team had any contact with Russian officials during the presidential campaign. "Of course not," he told Fox.

Leaders of the Senate Intelligence Committee said on Friday they will investigate alleged Russian attempts to influence the election and links between Russia and the political campaigns.