US director of national intelligence Dan Coats is leaving his job next month, ending a two-year tenure marked by President Donald Trump's clashes with intelligence officials.

Key points: Mr Trump has been critical of US intelligence officials throughout his time as President

Mr Trump has been critical of US intelligence officials throughout his time as President Mr Coats has been among the least visible of the President's senior officials but his statements have often been at odds with the administration's

Mr Coats has been among the least visible of the President's senior officials but his statements have often been at odds with the administration's The President has nominated congressman John Ratcliffe, a vocal Trump supporter, as his replacement

Mr Trump announced Mr Coats's August 15 departure in a tweet on Monday (AEST), in which he thanked Mr Coats for his service.

He said he would nominate Republican congressman John Ratcliffe for the post and name an acting official in the coming days.

Mr Ratcliffe has frequently defended Mr Trump, and he fiercely questioned former special counsel Robert Mueller last week during a House Judiciary Committee hearing.

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Mr Coats often appeared out of step with Mr Trump and disclosed to prosecutors how the President urged him to publicly deny any link between Russia and the Trump election campaign.

The frayed relationship reflected broader divisions between the President and the Government's intelligence agencies.

In a letter of resignation released on Sunday night (local time), Mr Coats said serving as the nation's top intelligence official had been a "distinct privilege" but that it was time for him to "move on" to the next chapter of his life.

He cited his work to strengthen the intelligence community's effort to prevent harm to the US from adversaries and to reform the security clearance process.

Mr Coats's public, and sometimes personal, disagreements with Mr Trump over policy and intelligence included Russian election interference and North Korean nuclear capabilities.

Mr Trump has long been sceptical of the nation's intelligence community, which provoked his ire by concluding that Russia interfered in the 2016 presidential election with the goal of getting him elected.

A former Republican senator from Indiana, Mr Coats was appointed director of national intelligence in March 2017, becoming the fifth person to hold the post since it was created in the wake of the 9/11 attacks to oversee and coordinate the nation's 17 intelligence agencies.

Coats's history of rebuking Trump

Mr Trump called Mr Coats to complain about the Mueller investigation. ( AP: Carolyn Kaster )

Mr Coats had been among the last of the seasoned foreign policy hands brought in to surround the President after his 2016 election victory, of whom the President steadily grew tired, officials said.

That roster included defence secretary Jim Mattis, secretary of state Rex Tillerson and later national security adviser H.R. McMaster.

Mr Coats developed a reputation inside the administration for sober presentations to the President of intelligence conclusions that occasionally contradicted Mr Trump's policy aims.

His departure had been rumoured for months, and intelligence officials had been expecting him to leave before the 2020 presidential campaign season reached its peak.

Mr Trump's announcement that Mr Coats would be leaving came days after Mr Mueller's public testimony on his two-year investigation into Russian election interference and potential obstruction of justice by Mr Trump, which officials said both emboldened and infuriated the President.

Mr Coats had been among the least visible of the President's senior administration officials but, in his limited public appearances, repeatedly seemed at odds with the administration, including about Russia.

For instance, he revealed to Mr Mueller's investigators how Mr Trump, angry over investigations into links between his campaign and Russia, tried unsuccessfully in March 2017 to get him to make a public statement refuting any connection.

"Coats responded that the Office of the Director of National Intelligence (ODNI) has nothing to do with investigations and it was not his role to make a public statement on the Russia investigation," Mr Mueller's report said.

Mr Trump later called Mr Coats to complain about the investigation and how it was affecting the Government's foreign policy.

Mr Coats told prosecutors he responded that the best thing to do was to let the investigation take its course.

In February, he publicly cast doubt on the prospects of persuading North Korea to end its nuclear weapons program despite the diplomatic efforts of the administration, which has touted its outreach to the isolated country as one of its most important foreign policy achievements.

Mr Coats, in testimony to Congress as part of annual national intelligence assessment, said North Korea would be "unlikely" to give up its nuclear weapons or its ability to produce them because "its leaders ultimately view nuclear weapons as critical to regime survival".

Mr Trump publicly bristled at the testimony of Mr Coats, the head of the CIA and other officials who contradicted his own positions on Iran, Afghanistan and Islamic State, as well as North Korea.

The intelligence officials were "passive and naive," he said in a tweet.

AP