WASHINGTON • Outgoing Central Intelligence Agency (CIA) chief John Brennan has launched a scathing attack on Mr Donald Trump, warning him to watch what he says and suggesting that the US President-elect does not understand the challenges posed by Russia.
Mr Brennan's stern words - which sparked a quick Twitter retort from Mr Trump - were the latest salvo in the feud between the incoming Republican leader and US intelligence agencies, which have concluded that Moscow meddled in last November's election.
"He's going to have the opportunity to do something for national security as opposed to talking and tweeting," said Mr Brennan.
"Spontaneity is not something that protects national security interests."
Mr Trump, who takes office on Friday, has been effusive in his praise of Mr Vladimir Putin, saying that if the Russian leader "likes" him, it would be an "asset" to help repair strained ties with Moscow.
The Senate Intelligence Committee, meanwhile, has launched a bipartisan probe into Moscow's alleged interference - which could force officials in both Mr Barack Obama's administration and Mr Trump's government to testify.
"I don't think he has a full appreciation of Russian capabilities, Russia's intentions and actions," Mr Brennan said of Mr Trump on Fox News on Sunday.
"I think Mr Trump has to be very disciplined in terms of what it is that he says publicly," he said.
"He is going to be, in a few days' time, the most powerful person in the world, in terms of sitting on top of the United States government, and I think he has to recognise that his words do have impact," the CIA chief said.
US intelligence agencies allege that Mr Putin ordered a covert effort to interfere in the election to boost Mr Trump and harm his opponent, Democrat Hillary Clinton.
A report from the director of National Intelligence released this month said hackers working for Russia penetrated Democratic Party computers and accounts to release files embarrassing to Mrs Clinton, and also conducted a campaign of media manipulation with the same aim.
Mr Trump's feud with intelligence agencies has been stoked by the leak of an unsubstantiated report that Russia had gathered compromising personal and financial material on the President-elect, and alleged close links between Trump and Kremlin aides during the campaign.
Hours after Mr Brennan's rebuke, Mr Trump slapped back on Twitter, echoing the words of Pulitzer Prize-winning journalist Bob Woodward, who called the alleged Russia "kompromat" dossier "garbage".
And later, he sent another tweet, this time slamming Mr Brennan for suggesting that Mr Trump did not fully understand Russia - and even seeming to hint that the CIA chief himself might have leaked the Russia dossier.
"Oh really, couldn't do much worse - just look at Syria (red line), Crimea, Ukraine and the build-up of Russian nukes. Not good! Was this the leaker of Fake News?" the tweet said.
Incoming Vice-President Mike Pence on Sunday dismissed suggestions that the Trump team and the Kremlin had made contact during the 2016 race.
"This is all a distraction," he said on NBC's Meet The Press.
AGENCE FRANCE-PRESSE, BLOOMBERG