CIA Director John Brennan implored US President-elect Donald Trump to put his confidence in the intelligence community and develop an "appreciation" for national security.

The Central Intelligence Agency chief defended his agency and said in a Sunday interview that the CIA was not trying to harm the incoming president or his team, CNN reported.

"There is no interest in undermining the President-elect and the team coming in. It's our responsibility to make sure they understand exactly the dangers that are out there," Brennan said.

Trump has slammed the intelligence community repeatedly over the past few weeks in response to what he said was unfair coverage caused by leaked information from intelligence officials.

First on Twitter and then at his first news conference since July, Trump likened the leaks to "Nazi Germany". Brennan called the Nazi reference "outrageous".

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

The CIA chief and formal deputy national security adviser to US President Barack Obama bristled at Trump's public displays of contempt for the intelligence community and said Trump needed to understand his words could undermine national security, CNN reported.

"If he doesn't have confidence in the intelligence community, what signal does that send to our partners and allies, as well as our adversaries?" Brennan said.

Brennan also warned Trump on Russia, saying he did not believe the real-estate mogul understood the threat of Moscow, while also saying he hoped the Trump administration would be able to see an improvement in the US-Russia relationship.