DANANG, Vietnam — President Trump said on Saturday that he believed President Vladimir V. Putin was sincere in his denials of interference in the 2016 presidential elections, calling questions about Moscow’s meddling a politically motivated “hit job” that was hindering cooperation with Russia on life-or-death issues.
Speaking after meeting privately with Mr. Putin on the sideline of the Asia Pacific Economic Cooperation summit meeting in Danang, Vietnam, Mr. Trump said that he had again asked whether Russia had meddled in the contest, but that the continued focus on the issue was insulting to Mr. Putin.
Mr. Trump said it was time to move past the issue so that the United States and Russia could cooperate on confronting the nuclear threat from North Korea, solving the Syrian civil war and working together on Ukraine.
“He said he didn’t meddle — I asked him again,” Mr. Trump told reporters traveling with him aboard Air Force One as he flew to Hanoi for more meetings. “You can only ask so many times. I just asked him again. He said he absolutely did not meddle in our election. He did not do what they are saying he did.”
Mr. Trump did not answer a direct question about whether he believed Mr. Putin’s denials, but his account of the conversation indicated he was far more inclined to accept the Russian president’s assertions than those of his own intelligence agencies, which have concluded that Mr. Putin directed an elaborate effort to interfere in the vote. The C.I.A., the National Security Agency, the F.B.I. and the Office of the Director of National Intelligence all determined that Russia meddled in the election.
“Every time he sees me he says, ‘I didn’t do that,’ and I really believe that when he tells me that, he means it,” Mr. Trump said of Mr. Putin. “I think he is very insulted by it, which is not a good thing for our country.”
His remarks came as the investigation into the Trump campaign’s ties to Russia deepened, with disclosures over the past two weeks showing that there were more contacts between Trump campaign advisers and Russians than were previously known, and that senior campaign officials were aware of them.
And the comments inspired immediate ridicule from Democratic lawmakers, including Representative Adam B. Schiff of California, the top Democrat on the House Intelligence Committee, which is investigating Russian interference in the election.
“You know who else is insulted by it, Mr. President? The American people,” Mr. Schiff said on Twitter. “You believe a foreign adversary over your own intelligence agencies.”
Representative Ted Lieu, another California Democrat, called Mr. Trump “dumb as a rock.” Mr. Lieu wrote on Twitter that both he and Mr. Trump had seen classified information on Russia’s interference in the election, and that Mr. Trump’s comments were lies.
“Trump knows the Kremlin hacked America last year,” Mr. Lieu said.
Senator John McCain of Arizona, chairman of the Senate Armed Services Committee, said in response to Mr. Trump’s statements, “There’s nothing ‘America First’ about taking the word of a K.G.B. colonel over that of the American intelligence community.”
Mr. Trump angrily dismissed the criticism in a tweet on Sunday morning.
“When will all the haters and fools out there realize that having a good relationship with Russia is a good thing, not a bad thing,” he wrote, adding that critics were “playing politics — bad for our country.”
“I want to solve North Korea, Syria, Ukraine, terrorism,” he added, “and Russia can greatly help!”
Mr. Trump also heaped disdain on the former leaders of three American intelligence agencies — John O. Brennan, the former C.I.A. director; James R. Clapper Jr., the former director of national intelligence; and James B. Comey, the F.B.I. director he fired this year — appearing to suggest that they were less trustworthy than Mr. Putin.
“I mean, give me a break — they’re political hacks,” Mr. Trump said. “You have Brennan, you have Clapper, and you have Comey. Comey’s proven now to be a liar, and he’s proven to be a leaker, so you look at that. And you have President Putin very strongly, vehemently says he had nothing to do with that.”
The Central Intelligence Agency on Saturday declined to comment on the remarks by President Trump about Russian interference in the election.
Last week, in response to questions about the views of the director, Mike Pompeo, on the intelligence assessment, the C.I.A. said “the director stands by, and has always stood by, the January 2017 Intelligence Community Assessment.”
But since taking over the agency after being appointed by Mr. Trump, Mr. Pompeo has, at times, sought to downplay the Russian interference in the election. At a public appearance last month, he said that the intelligence assessment had found that Russia’s interference did not affect the outcome of the election.
In fact, the assessment stated that it did not address whether Russia had any impact on vote’s outcome. “We did not make an assessment of the impact that Russian activities had on the outcome of the 2016 election,” the assessment said.
The president said lingering questions about whether his campaign aides had worked with Russia to sway the election were souring Washington’s relationship with Moscow on a host of vital security issues.
“Having a good relationship with Russia is a great, great thing,” Mr. Trump said. “This artificial Democratic hit job gets in the way, and that’s a shame, because people will die.”
The allegations of collusion are the subject of an investigation by the special counsel Robert S. Mueller III, as well as multiple congressional inquiries.
Mr. Trump’s comments about the Russian president and his warning about deteriorating Moscow ties came after the close of the APEC conference in Danang, where the White House steered clear of a formal meeting between the two men and made a point of announcing on Friday that one would not occur.
Reporters who travel with Mr. Trump were barred from covering his activities for most of Saturday, leaving them in the dark about his informal interactions. But video showed him shaking hands with Mr. Putin on Friday at a gala dinner and chatting with him on Saturday before and after a group photograph of the APEC leaders.
The Kremlin released a statement saying that the leaders had met and struck an agreement on Syria, but the White House did not immediately confirm the information. Speaking with reporters later, Mr. Trump said he had two or three brief conversations with Mr. Putin, mostly about Syria.
The talks were described in a joint statement by United States and Russia that reaffirmed previous commitments to defeat the Islamic State and to untangle conflicts between their forces on the Syrian battlefield.
It said that Mr. Trump believed he had “a good meeting” with Mr. Putin on common efforts that, once in place, would “save thousands of lives.”
Mr. Trump’s description of the exchange about election meddling was striking because it suggested that he concurred with Mr. Putin’s oft-stated contention that the issue was a contrived story that had been allowed to become a detriment to both the United States and Russia.
“This is really an artificial barrier that’s put in front of us for solving problems with Russia,” Mr. Trump said of Mr. Putin. “He says that very strongly; he really seems to be insulted by it, and he says he didn’t do it.”
Mr. Trump’s reaction recalled the first face-to-face talk between the two presidents, on the sideline of the Group of 20 summit meeting in July in Hamburg, Germany, during which Mr. Trump broached the subject of Russia’s election meddling but threatened no consequences.
When Mr. Putin denied meddling, American officials said at the time, Mr. Trump said the two countries must agree to disagree on the issue and move on to other topics where they could work together.
Russian officials provided an alternative account, asserting at the time that Mr. Trump had accepted Mr. Putin’s denial of the election interference and even said that some in the United States were “exaggerating” Moscow’s role without proof.
That seemed to have been Mr. Trump’s message on Saturday, when he repeatedly blamed Democrats for allegedly harming his efforts to improve relations with Russia by pushing false charges.
“I call it the artificial Democrat barrier that gets in the way,” Mr. Trump said. “Which is a shame.”
Mr. Putin similarly brushed off recent revelations that Russians had contacts with Mr. Trump’s campaign team — including an aide who had met with a woman described as Mr. Putin’s niece — as a “domestic political struggle” in the United States.
“I think that everything connected with the so-called Russian dossier in the United States is a manifestation of a continuing domestic political struggle,” Mr. Putin said after the summit meeting, in remarks carried by Russian news media.
“I learned only yesterday about some sort of meeting of my relatives with representatives of the administration or official figures,” Mr. Putin said. He said his press secretary, Dmitry Peskov, had told him about the reports.
“I know absolutely nothing about this — absolutely nothing,” Mr. Putin said. “It seems like nonsense.”
He told reporters in Danang, “It’s important that we find an opportunity, with our teams, to sit down at the level of presidents and talk through our complex relations.” He added: “Our relations are still in crisis. Russia is ready to turn the page and move on.”
Mr. Putin said a scheduling conflict and an unspecified issue with protocol had gotten in the way of a more substantive meeting with Mr. Trump. “This was connected to Mr. Trump’s schedule, and my schedule, and certain formalities with protocol that our teams, unfortunately, didn’t resolve. Well, they will be punished,” he said.
“Still, nothing terrible happened,” Mr. Putin added. “We spoke in the course of today’s gathering; we had a conversation.”
Mr. Putin said that Mr. Trump behaved at meetings “with the highest level of good will and correctness,” adding, “He is a cultured person, and comfortable discussing matters related to work.”