Kim Jong-un has been formally named head of state of North Korea and commander in chief of the military in a new constitution observers said was possibly aimed at preparing for a peace treaty with the US.

North Korea has also long called for a peace deal with the US to normalize relations and end the technical state of war that has existed since the 1950-1953 Korean War concluded with an armistice rather than a peace treaty.

The new constitution, unveiled on the Naenara state portal site on Thursday, said that Kim as chairman of the State Affairs Commission, a top governing body created in 2016, was "the supreme representative of all the Korean people," which means head of state, and "commander in chief."

A previous constitution simply called Kim "supreme leader" who commands the country's "overall military force."

Hong Min, a senior researcher of the Korea Institute for National Unification in Seoul, said the title change was also aimed at preparing for a potential peace treaty with the US.

"The amendment may well be a chance to establish Kim's status as the signer of a peace treaty when it comes," Hong said.

Washington had balked at signing a comprehensive peace treaty before North Korea takes substantial steps toward denuclearization, but US officials have signaled they may be willing to conclude a more limited agreement to reduce tensions, open liaison offices, and move toward normalizing relations.

Denuclearization talks between the US and North Korea have stalled, although fresh talks with Pyongyang are supposed to take place this month.

North Korea has frozen nuclear bomb and long-range missile testing since 2017. 

The new constitution continued to describe North Korea as a nuclear weapons state.