Donald Trump says the top US spy called him to “denounce” allegations that Russian intelligence have compromising information about the president-elect.
Mr Trump tweeted that the unverified claims were “false and fictitious”.
Director of National Intelligence James Clapper said on Wednesday evening that the intelligence community had made no judgment on whether they were reliable.
Mr Clapper also said he had rejected Mr Trump’s suggestion that US intelligence was responsible for leaking the claims.
The spymaster said both men had agreed the security breach was “extremely corrosive and damaging to our national security”.
Mr Clapper said he had also assured the president-elect the intelligence community “stands ready to serve his administration”.
Intelligence agencies considered the claims relevant enough to brief both Mr Trump and President Barack Obama last week.
In his first news conference as president-elect on Wednesday, Mr Trump said it would be a “tremendous blot” on the reputation of US intelligence agencies if they had been responsible for the leak from the briefing.
“That’s something that Nazi Germany would have done,” he said.
Mr Trump also robustly denied the claims to journalists at Trump Tower in New York, describing them as “fake news” and “crap”.
The 35-page dossier of allegations – which was circulating in political and media circles before November’s presidential election – was published in full on Buzzfeed on Tuesday evening.
It claims Russia has damaging information about the president-elect’s business interests, and footage of him using prostitutes at the Ritz-Carlton hotel in Moscow.
Russia also strongly denied the allegations as “pulp fiction”.
