"Considering the source of the criticism, I consider that criticism a badge of honor," former CIA chief John Brennan told CNN's State of the Union, where he appeared alongside former Director of National Intelligence James Clapper.
"I found it particularly reprehensible that on Veterans Day, Donald Trump would attack and impugn the integrity and the character of Jim Clapper, who served in uniform for 35 years," said the ex-CIA chief.
"I think it's something Mr. Trump should be ashamed of," he added.
Trump, now in the Philippines at the end of a 12-day Asia tour, had lashed out at Brennan, Clapper and former FBI director James Comey after facing stiff criticism at home for saying he believed President Vladimir Putin was sincere in insisting that Russia had not interfered in the US election.
'He means it'
"I really believe that when he tells me that, he means it," Trump said later aboard Air Force One.
But then in a surprising attack - especially from a president traveling abroad - Trump suggested that he placed greater credibility in Putin's assurances than in the endorsement by Brennan, Clapper and Comey of the US intelligence agencies' finding of Russian interference.
"I mean, give me a break -- they're political hacks," Trump said, naming the three men and blaming Democrats for the talk of Russian collusion with his election campaign.
He said Comey, whom he fired in May as pressure was building over the Russia allegations, was "a liar," and he reiterated that Putin had "vehemently" denied any meddling.
U.S. President Donald Trump boards Air Force One before departing from Noi Bai international airport, in Hanoi, Vietnam Sunday, Nov. 12, 2017. Source: AAP
Brennan and Clapper pushed back hard on Sunday, describing Trump's tepid response to the alleged Russian meddling as endangering US national security.
"Putin is committed to undermining our system, our democracy and our whole process," Clapper said. "And to try to paint it in any other way is, I think, astounding and, in fact, poses a peril to this country."
Brennan added: "I think he's giving Putin a pass. And I think it demonstrates to Mr. Putin that Donald Trump can be played by foreign leaders who are going to appeal to his ego and to try to play upon his insecurities. Which is very, very worrisome."
On Sunday, Trump revised his initial criticism a bit, saying of the Russian meddling charges: "As to whether I believe it or not, I'm with our agencies, especially as currently constituted with their leadership," a phrase that excludes Clapper, Brennan and Comey.
But one of the current leaders, CIA director Mike Pompeo - a Trump appointee - has reiterated his support for the finding of Russian interference.