US President Donald Trump says he is considering five very qualified people to replace John Bolton as his national security adviser.

Speaking to reporters at the White House, Trump said Bolton, who he abruptly fired on Tuesday, had made some mistakes, including offending North Korea’s leader Kim Jong-un by demanding that he follow a “Libyan model” and hand over all his nuclear weapons.

Trump said there were a lot of people interested in Bolton’s position.

“There are five people that I consider very highly qualified,” he said, without naming them. “We’ll be announcing somebody next week, but we have some very highly qualified people.”

He said he got along well with Bolton and hoped they parted on good terms but added that the former adviser was out of line on Venezuela, which has been another of the administration’s top foreign policy challenges.

While the two were mostly in sync on the need to push Venezuelan President Nicolas Maduro from power, Trump had become increasingly impatient at the failure of a US-led campaign of sanctions and diplomacy to remove the socialist leader.

Trump declined to comment on Wednesday on whether he would meet with Maduro.

Trump was asked whether he would consider easing sanctions on Iran to secure a meeting with its leader President Hassan Rouhani at this month’s UN General Assembly and replied: “We’ll see what happens.”

Separately, Rouhani said Tehran would not negotiate with Washington while sanctions on his country are still being enforced by the US.

Trump and US Secretary of State Mike Pompeo have said the president is open to meeting with Rouhani.

Asked if he is looking at such a meeting, Trump told reporters on Wednesday that he is not looking at anything.

North Korea has denounced Bolton as a “war maniac” and “human scum”.

Bolton has proposed using military force to overthrow the ruling Kim family and US officials have said he was responsible for the collapse of Trump and Kim’s second summit in Vietnam in February.

Efforts to engage with North Korea nearly fell apart after Trump followed Bolton’s advice in Hanoi and handed Kim a piece of paper that bluntly called for the transfer of Pyongyang’s nuclear weapons and bomb fuel to the US.

The document effectively reprised Bolton’s long-held “Libya model” of unilateral denuclearisation that North Korea has repeatedly rejected and that analysts said would have been seen by Kim as insulting and provocative.

Trump announced he had fired Bolton a day after North Korea signalled a new willingness to resume stalled denuclearisation talks but then proceeded with the latest in a spate of missile launches.

Analysts say Bolton’s removal could help US efforts to revive the talks but will not make Washington’s aim of persuading Pyongyang to give up its nuclear weapons any easier.

-AAP