Two former US intelligence chiefs say Donald Trump’s stance on Russian meddling in last year’s presidential election is putting the US at risk.
The US president sparked uproar by suggesting he believed Russian counterpart Vladimir Putin when he said there had been no interference.
The two leaders briefly discussed the allegations at an Asia-Pacific summit.
US intelligence has long concluded Russia tried to sway the vote in Mr Trump’s favour.
“Every time he [Putin] sees me he says I didn’t do that, and I really believe that when he tells me that, he means it,” Mr Trump told reporters.
“I think he is very insulted by it, which is not a good thing for our country.”
Mr Trump also disparaged key figures in the US intelligence community who concluded in January that Russian meddling had taken place, including former national intelligence chief James Clapper, ex-CIA director John Brennan and sacked FBI chief James Comey, whom he called “political hacks”.
Mr Trump has since sought to mollify critics of his comments following uproar at his apparent defence of Mr Putin.
Ex-intelligence chiefs go on the attack
Mr Clapper said he was alarmed by the president’s comments.
“Putin is committed to undermining our system, our democracy and our whole process,” he told CNN.
“To try to paint it in any other way is, I think, astounding and in fact poses a peril to this country.”
Appearing alongside him, Mr Brennan, said he found it “puzzling” why Mr Trump was not more explicit in condemning the Russian president when it represented a “national security problem”.
Referring to Mr Trumps criticism of him, Mr Brennan said: “Considering the source of the criticism, I consider that criticism a badge of honour.”
Why the row matters
Questions surrounding Russia’s role in last year’s US elections and allegations of collusion involving Donald Trump’s campaign team have dogged his presidency.
US intelligence agencies believe Russia tried to help Mr Trump win the presidency by hacking and releasing emails damaging to his opponent Hillary Clinton.
While Russian hackers are widely suspected of involvement, there has been no conclusive link to the Kremlin.
Special counsel Robert Mueller is currently investigating whether there were any links between Russia and the Trump campaign. Both deny there was any collusion.
Last month, former Trump campaign adviser George Papadopoulos pleaded guilty to having lied to the FBI about the timing of meetings with alleged go-betweens for Russia.
Mr Trump’s former campaign manager, Paul Manafort, and an associate were also placed under house arrest on charges of money laundering as a result of the Mueller inquiry, but the charges do not relate to the election.