Donald Trump steps up to bat for Vladimir Putin

US President Donald Trump and Russian President Vladimir Putin shake hands at the APEC Summit in Danang, Vietnam. Photo / Supplied

United States President Donald Trump said that President Vladimir Putin had assured him again that Russia did not interfere in the 2016 presidential campaign, and indicated that he believed Putin's sincerity, drawing immediate criticism from lawmakers and former intelligence officials responsible who assessed that the meddling took place.

"I asked him again," Trump said after what he described as several brief, informal chats with Putin in Danang, Vietnam, where they were attending a regional conference. "You can only ask so many times ... He said he absolutely did not meddle in our election. He did not do what they are saying he did.

"I really believe that when he tells me that, he means it ... I think he's very insulted, if you want to know the truth," Trump told reporters travelling with him aboard Air Force One from Danang to Hanoi.

Trump voiced similar conclusions after his only previous meeting with Putin, last July in Germany.

It was a jarring return to the more insular preoccupations of Washington after more than a week of pageantry and pledges of mutual admiration, but few substantive outcomes, between Trump and Asian leaders.

Trump suggested that what he called the "artificial Democratic hit job" of investigations of possible collusion between his campaign and Russia were somehow preventing US-Russia cooperation on a range of issues, including North Korea. "It's a shame," he said, "because people will die because of it."

In his own news conference after their talks, Putin said he knew "absolutely nothing" about Russian contacts with Trump campaign officials.

"They can do what they want, looking for some sensation," Putin said of the investigations. "But there are no sensations."

Trump described the former top US intelligence officials who concluded in January that the tampering took place - including former director of national intelligence James Clapper and former CIA director John Brennan - as "political hacks". He called former FBI Director James Comey, who testified before Congress that Trump asked him to drop an investigation of his campaign's connections to Russian officials, a proven "liar" and a "leaker".

Clapper said: "The fact that he would take Putin at his word over the intelligence community is unconscionable". Senator John McCain said: "There's nothing 'America First' about taking the word of a KGB colonel over that of the American intelligence community ... Vladimir Putin does not have America's interests at heart. To believe otherwise is not only naive but also places our national security at risk."

Trump said in his airborne remarks to reporters that a statement by Chinese President Xi Jinping calling for the denuclearisation of North Korea, which depends on China for its economic survival, was a major step forward that "a lot of people ... didn't pick up".

During his trip to the Asia region, Trump's "America First" slogan has, in many ways, begun to translate into something more akin to America alone.

The 11 nations which had once looked to American leadership to seal the deal on the Trans-Pacific Partnership moved on without the US and announced a tentative agreement among themselves. It marked a stunning turnabout that foreign policy analysts warned could further erode US standing at a time when China is embarked on a major economic expansion and further undermine global confidence in America's ability to organise the world around its own liberal values.