A day after he lashed out at US intelligence agency chiefs over their assessments of global threats, President Donald Trump abruptly reversed course and said that he and the intelligence community "are all on the same page".

Trump met with his director of national intelligence and other top security officials in the Oval Office on Thursday and said afterward that they told him their testimony at a Senate hearing had been "mischaracterised" by the news media.

House Speaker Nancy Pelosi and other Democrats had slammed the president for his comments disparaging Director of National Intelligence Daniel Coats, Central Intelligence Agency (CIA) Director Gina Haspel and other top security officials.

The officials told Congress on Tuesday that North Korea is unlikely to dismantle its nuclear arsenal and that the Iran nuclear deal is working, contrary to what Trump has claimed.

The intelligence agency chiefs "said that they were totally misquoted and ... it was taken out of context," Trump told reporters at the White House. "They said it was fake news."

Coats and other officials presented an update to the Senate intelligence committee on Tuesday on their annual assessment of global threats.

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In a public report and testimony broadcast on C-SPAN, they warned of an increasingly diverse range of security dangers around the globe, from North Korean nuclear weapons to Chinese cyber espionage to Russian campaigns to undermine Western democracies.

Trump tweeted Thursday that he and the intelligence leaders "are very much in agreement on Iran, ISIS, North Korea, etc." and that he values their service.

"Happily, we had a very good meeting, and we are all on the same page!" he wrote.

Pelosi told reporters that the intelligence officials were "courageous" in speaking "truth to power" by publicly contradicting Trump.

"One dismaying factor of it all is that the president just doesn't seem to have the attention span or the desire to hear what the intelligence community has been telling him," Pelosi said on Thursday, calling Trump's comments attacking the intelligence leaders "cause for concern."

Trump said earlier that intelligence officials were wrong about North Korea, Iran and the militant Islamic State group, which they said remains a terrorist and insurgent threat.

“Perhaps Intelligence should go back to school!” Trump tweeted Wednesday.

Pelosi said Trump's comments were "stunning".

"It's important for the Republicans in Congress to recognise they have to weigh in with the president to say, 'You can't act without knowledge,'" Pelosi said.

Senate Democratic leader Chuck Schumer said it was "past time" for US intelligence officials to stage an intervention with Trump.

In a letter to Coats, Schumer called Trump's criticism of intelligence agencies "extraordinarily inappropriate" and said it could undermine public confidence in the government's ability to protect Americans.

Schumer urged Coats and other officials to "educate" Trump about the facts and raw intelligence underlying threat assessments so the administration can speak "with a unified and accurate voice about national security threats."

Asked about his tweets earlier on Thursday, Trump did not back away from questioning the assessment by Coats and Haspel.

"I disagree with certain things that they said. I think I'm right, but time will prove that, time will prove me right probably," Trump told reporters at the White House.

"I think Iran is a threat. I think I did a great thing when I terminated the ridiculous Iran nuclear deal. It was a horrible one-sided deal."

Speaking about intelligence agencies generally, Trump added: "I have great respect for a lot people but I don't always agree with everybody."

At a hearing on Tuesday, Coats had said intelligence information does not support the idea that North Korean leader Kim Jong Un will eliminate his nuclear weapons.

Trump later insisted on Twitter that the US relationship with North Korea "is the best it has ever been".

He pointed to the North's halt in nuclear and missile tests, the return of some US service members' remains and the release of detained Americans as signs of progress.

US intelligence agencies also said Iran continues to work with other parties to the nuclear deal it reached with the US and other world powers.

In doing so, they said, Iran has at least temporarily lessened the nuclear threat. In May 2018, Trump withdrew the US from that accord, which he said would not deter Iran.

"The Intelligence people seem to be extremely passive and naive when it comes to the dangers of Iran," Trump tweeted. "They are wrong!"