North Korean leader Kim Jong-un has said there is no reason for the country to avoid dialogue with the US if Washington stops insisting that his country give up nuclear weapons, state news agency KCNA reported.

In a speech at the Supreme People's Assembly on Sunday, Kim said he still has fond memories of US President Donald Trump, KCNA also reported. The two leaders met three times during Trump's first presidency.

"If the United States drops the absurd obsession with denuclearising us and accepts reality, and wants genuine peaceful coexistence, there is no reason for us not to sit down with the United States," Kim was quoted as saying.

It was a matter of survival for the country to build nuclear weapons to safeguard its security in the face of grave threats from the United States and South Korea, Kim said.

He said he rejected recent overtures from Washington and Seoul for dialogue as insincere because their fundamental intent to weaken the North and destroy his regime remains unchanged.

He said a proposal by the South on ending the North's nuclear programmes in phases was proof of that.

Peace overtures

South Korean President Lee Jae Myung has made peace overtures since taking office in June, saying dialogue with Pyongyang was necessary, and has proposed steps to build confidence and eventually end the North's nuclear programme.

It was necessary to create the right conditions to bring the North back to the table, and Trump has a key role to play in those efforts, Lee said.

Analysts say Kim's nuclear push is aimed at eventually pressuring Washington to accept the idea of the North as a nuclear power and to negotiate economic and security concessions from a position of strength.

Kim is also trying to bolster his leverage by strengthening cooperation with traditional allies Russia and China, in an emerging partnership aimed at undercutting US influence.

There's growing concern in Seoul that it could lose its voice in future efforts to defuse the nuclear standoff on the peninsula, as the North seeks to negotiate directly with the United States. Such fears were amplified last year when Kim declared that he was abandoning North Korea's long-standing goal of peaceful unification with South Korea and ordered a rewriting of the North’s constitution to cement the South as a permanent enemy.