Iran more destabilising than N Korea: Pompeo

US Secretary of State Mike Pompeo underlined the need for different foreign policy approaches to Iran and North Korea in comments published Thursday, describing Tehran as more "destabilising" than Pyongyang.

"We've made very clear that these situations are very different. We take each of them where we find them," he told US television station CBS in excerpts of a transcript released by the State Department.

Washington set 12 tough conditions on talks with Iran, yet President Donald Trump made almost no stipulations on meeting North Korean leader Kim Jong Un last year and the White House has had follow-up contacts with the regime.

"North Korea today has weapons, nuclear weapons, capable of reaching the United States of America," Pompeo said.

"This is a threat that President Trump said we needed to take on now and take on immediately. The president's chosen to meet with Chairman Kim."

Trump and Kim are due to follow their landmark first summit in Singapore last June with a meeting in Hanoi from February 27 to 28.

"North Korea behaves very differently. They're not destabilising Yemen. They're not destabilising Syria. They're not conducting enormous assassination campaigns," Pompeo said.

"These countries' behaviours are different, therefore, the way America is approaching resolving this."

The US administration has repeatedly accused North Korea in recent years of destabilising its East Asian neighbours with its nuclear arms race and missiles pointed toward Seoul.

Meanwhile, 12 North Korean officials -- including Kim Jong Un's de-facto chief of staff -- were en-route to Vietnam yesterday ahead of the summit between Kim and Trump, South Korea's Yonhap news agency said.