US President Donald Trump says he believes Russian President Vladimir Putin believes it when he says Moscow did not interfere in the 2016 US presidential election, but Mr Trump says he also believes US intelligence agencies which concluded Russia did.

Key points: Mr Trump had earlier said he believed Mr Putin was being genuine

Mr Trump had earlier said he believed Mr Putin was being genuine He also described former US intelligence officials as "political hacks"

He also described former US intelligence officials as "political hacks" Mr Trump today said he believes the assessment made by US intelligence on Russia

"I believe that he feels that he and Russia did not meddle in the election," Mr Trump said of Mr Putin at a news conference with Vietnam's President Tran Dai Quang in Hanoi.

"As to whether I believe it, I'm with our agencies."

Speaking to reporters aboard Air Force One earlier, Mr Trump had said Mr Putin had again vehemently denied the allegations, this time during an economic summit in Vietnam.

Mr Trump said he believed "that when he tells me that, he means it."

Mr Trump had also dismissed former US intelligence officials as "political hacks" and accused Democrats of using the issue to try to sabotage relations between the two countries, putting lives at risk.

However speaking at the news conference in Hanoi, Mr Trump backed away from those comments.

"As currently led by fine people, I believe very much in our intelligence agencies," he added.

Mr Trump also reiterated his view that it's crucial for the US to get along with Russia, and seemed to suggest it was time to remove the sanctions Congress has slapped on Russia in retaliation for its election meddling efforts.

"It's now time to get back to healing a world that is shattered and broken," Mr Trump said.

"Those are very important things."

But there appeared to be little progress in US-Russia relations, with the Kremlin blaming the US for the lack of a bilateral meeting between Mr Trump and Mr Putin in Vietnam.

The two met briefly on the sidelines of the Asia-Pacific Economic Cooperation summit but did not hold substantive bilateral talks.

"Unfortunately the American side did not offer any alternatives despite all efforts of our Russian colleagues," Kremlin spokesman Dmitry Peskov was quoted as saying by the RIA news agency.

"There was only one time offered that was convenient for the American side, and only one place offered, which had already been rented by the Americans.

"The Americans showed no flexibility, and unfortunately did not offer any other alternative proposals."

Trump appears to contradict Putin comments

Mr Trump says in his view it's crucial for the US to get along with Russia. ( Reuters: Sputnik/Mikhail Klimentyev/Kremlin )

As he travelled to Hanoi, the second-to-last stop of his Asia trip, Mr Trump told reporters Mr Putin "said he absolutely did not meddle in our election. He did not do what they are saying he did."

"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, calling the accusation an "artificial barrier" erected by Democrats.

The president lashed out at the former heads of the nation's intelligence community, and said there were plenty of reasons to be suspicious of their findings.

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"I mean, give me a break. They're political hacks," Mr Trump said, citing by name James Clapper, the former director of national intelligence, John Brennan, the former CIA director and his ousted ex-FBI director James Comey, whom Mr Trump said was "proven now to be a liar and he's proven to be a leaker."

In a tweet sent from Hanoi, Mr Trump bashed the "haters and fools" he said are questioning his efforts to improve relations with Russia and accused critics of "playing politics" and hurting the country.

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His comments about Mr Putin and "political hacks" brought criticism from politicians with ties to the intelligence community.

Senator John McCain, the Republican Party's presidential nominee in 2008, said in a statement that Mr Trump's faith in Mr Putin's denial was "naive".

Mr Trump was in Hanoi for a brief state visit, including Sunday's meeting with Mr Tran at the presidential palace.

In brief remarks after his arrival, Mr Trump offered help negotiating with China on disputes over the South China Sea.

Beijing's island-building there has drawn criticism from Washington, which argues the US has a national interest in freedom of navigation in sea lanes critical for world trade.

US Secretary of State Rex Tillerson earlier this month said China's "provocative actions" challenged international law and norms.

"If I can help mediate or arbitrate, please let me know," Mr Trump offered.

"I'm a very good mediator and a very good arbitrator. I've done plenty of it from both sides."

Mr Trump's comments on Mr Putin and the Russia investigation attracted criticism. ( Jorge Silva: AP )

Reuters