Outgoing CIA Director John Brennan has issued a stern parting rebuke to Donald Trump days before he assumes the US presidency.
Mr Brennan has advised the incoming president not to absolve Russia for its recent actions.
Mr Brennan's comments, in an interview on Fox News Sunday, laid bare the simmering tensions between Mr Trump and the intelligence community he has criticised and is on the verge of commanding.
The CIA director said Mr Trump needs to be mindful about his off-the-cuff remarks once he takes the oath of office on Friday, alluding to his penchant for making broad pronouncements on Twitter.
"Spontaneity is not something that protects national security interests and 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," Brennan said.
"It's more than just about Mr Trump. It's about the United States of America."
Mr Trump last week accused the intelligence community of leaking information about an unsubstantiated report on compromising information the Russians have accumulated against the Republican Party leader.
On Twitter, he accused intelligence agencies of practices reminiscent of Nazi Germany.
"What I do find outrageous is equating intelligence community with Nazi Germany," Mr Brennan said. "I do take great umbrage at that."
Mr Brennan also questioned the message it sends to the world if the president-elect broadcasts he does not have confidence in the United States' own intelligence agencies.
For months, Mr Trump had publicly doubted US intelligence conclusions that Russia was behind cyber attacks against Democratic political groups before saying in a news conference on Wednesday that he thinks Russia was behind the hacking.