North Korea has threatened to resume calling US President Donald Trump a “dotard” if he keeps using provocative language about its leader.

Choe Son Hui, North Korea’s first vice-foreign minister, issued the warning days after Mr Trump spoke of possible military action toward the isolated regime and revived his “Rocket Man” nickname for ruler Kim Jong-un.

The comments came as prospects dim for a resumption of nuclear diplomacy between the two countries.

Mr Choe said Mr Trump’s remarks “prompted the waves of hatred of our people against the US” because they showed “no courtesy when referring to the supreme leadership of dignity” of North Korea.

“If any language and expressions stoking the atmosphere of confrontation are used once again … that must really be diagnosed as the relapse of the dotage of a dotard,” Mr Choe said.

During a visit to London on Tuesday, Mr Trump said his relationship with Mr Kim was “really good” but also called for him to follow up on a commitment to denuclearise.

Mr Kim, Mr Trump added, “likes sending rockets up, doesn’t he? That’s why I call him Rocket Man”.

In 2017, Mr Trump and Mr Kim traded threats of destruction as North Korea carried out a slew of high-profile weapons tests aimed at acquiring an ability to launch nuclear strikes on the US mainland.

Mr Trump said he would rain “fire and fury” on North Korea and derided Mr Kim as “little Rocket Man”, while Mr Kim questioned Mr Trump’s sanity and said he would “tame the mentally deranged US dotard with fire”.

The two leaders have avoided such words and developed better relations after North Korea entered nuclear negotiations with the US last year. Mr Trump even said he and Mr Kim “fell in love.”

But nuclear diplomacy between the two countries has remained largely deadlocked since their second meeting in Vietnam in February ended abruptly and without any deal, due to disputes over US-led sanctions on North Korea.

-AAP