HANOI, Vietnam -- President Trump said Russia's Vladimir Putin once again vehemently denied interfering in the 2016 U.S. elections during their discussions on the sidelines of an economic summit Saturday. Mr. Trump made clear he's not interested in dwelling on the issue.

"He said he absolutely did not meddle in our election. He did not do what they are saying he did," Mr. Trump said of Putin, speaking with reporters aboard Air Force One as he traveled to Hanoi, the second-last stop of his Asia trip.

"Every time he sees me, he said: 'I didn't do that.' And I believe, I really believe that when he tells me that he means it," Mr. Trump said, noting that Putin is "very insulted" by the accusation. Mr. Trump called the accusation an "artificial barrier" erected by Democrats -- once again casting doubt on the U.S. intelligence community's conclusion that Russia did try to interfere in the election to help Mr. Trump win.

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Mr. Trump and Putin did not have a formal meeting while they were in Vietnam for the Asia-Pacific Economic Cooperation summit, but the two spoke informally several times on the event's sidelines and reached an agreement on a number of principles for the future of war-torn Syria.

President Trump takes questions from reporters en route to Hanoi, Vietnam, aboard Air Force One on Nov. 11, 2017. Reuters

Mr. Trump's latest comments contrast with those of current and former U.S. intelligence officials, including CIA Director Mike Pompeo who has said Russia "clearly" meddled in the 2016 election, and has been meddling in elections for a hell of a long time."

But Mr. Trump made clear that the issue of Russian meddling in the election hovers over the leaders' relationship and said it jeopardized their ability to work together on issues including North Korea's escalating nuclear program and the deadly conflict in Syria.

"Having a good relationship with Russia's a great, great thing. And this artificial Democratic hit job gets in the way," Mr. Trump told reporters. "People will die because of it."

Mr. Trump danced around the question of whether he believed Putin's denials, telling reporters that pressing the issue would have accomplished little.

"He said he didn't meddle. I asked him again. You can only ask so many times," said Mr. Trump.

"Well, look, I can't stand there and argue with him," he added later. "I'd rather have him get out of Syria, to be honest with you. I'd rather have him, you know, work with him on the Ukraine than standing and arguing about whether or not -- cause that whole thing was set up by the Democrats."

Mr. Trump's suggestion that he may believe Putin over his own nation's intelligence community is certain to reignite the firestorm over the issue of election meddling. Meanwhile, a special counsel investigation of potential collusion between Moscow and Trump campaign aides so far has resulted in two indictments for financial and other crimes unrelated to the campaign, as well as a guilty plea. Congressional committees have also been interviewing campaign and White House staff.

Earlier Saturday, the Kremlin issued a statement saying the leaders had reached agreement on a number of principles for the future of civil war-torn Syria now that the Islamic State of Iraq and Syria (ISIS) has largely been pushed out. Among the agreements' key points, according to the Russians, were an affirmation of de-escalation zones, a system to prevent dangerous incidents between American and Russian forces, and a commitment to a peaceful solution governed by a Geneva peace process.

The Kremlin quickly promoted the agreement as the White House stayed silent. Mr. Trump told reporters that the deal was reached "very quickly" and that it would save "tremendous numbers of lives." And he praised his relationship with Putin the two "seem to have a very good feeling for each other and a good relationship, considering we don't know each other well."

Snippets of video of from the summit in the sea-side city of Danang showed Mr. Trump and Putin shaking hands and chatting, including during the world leaders' traditional group photo. The two walked together down a path to the photo site, conversing amiably, with Mr. Trump punctuating his thoughts with hand gestures and Putin smiling.

Journalists traveling with Mr. Trump were not granted access to any of the APEC events he participated in in the picturesque tropical seaside city Saturday.

White House officials had worked quietly behind the scenes negotiating with the Kremlin on the prospect of a formal meeting. The Russians raised expectations for such a session and Mr. Trump told reporters aboard Air Force One en route to Asia that it was "expected we'll meet with Putin" to discuss issues including ramping up pressure on North Korea to halt its nuclear and ballistic weapons program. As speculation built, the two sides tried to craft the framework of a deal on the future of Syria that Mr. Trump and Putin could announce in a formal bilateral meeting, according to two administration officials not authorized to speak publicly about private discussions.

Though North Korea and the Ukraine had been discussed, the two sides focused on trying to strike an agreement about a path to resolve Syria's civil war once ISIS is defeated, according to officials. But the talks stalled and, minutes before Air Force One touched down in Vietnam, White House press secretary Sarah Huckabee Sanders told reporters the meeting was off.

Mr. Trump will be attending a state dinner in Hanoi Saturday night. On Sunday, he'll meet with the country's president and prime minister before heading to his last stop: The Philippines.

CBS News' Stefan Becket and Kathryn Watson contributed to this report.