"Kim Jong Un said that the DPRK's will for denuclearisation of the Korean peninsula still remains unchanged and consistent and fixed," KCNA reported after their meeting in Pyongyang on Thursday.

Kim hoped US-North Korean relations and denuclearisation of the peninsula "will be solved on a stage-by-stage basis" and "he hoped that the solution of the issues will progress through effective and constructive dialogue and negotiation," the report by the North Korean news agency said.

Lavrov's visit came as US Secretary of State Mike Pompeo and a top North Korean official held talks on planning a historic summit between Kim and President Donald Trump in Singapore.

The key task ahead of the June 12 summit is to settle the agenda. The main stumbling block is likely to be the concept of "denuclearisation" -- both sides say they are in favour of it, but there is a yawning gap between their definitions.

Washington wants North Korea to quickly give up all its nuclear weapons in a verifiable way in return for sanctions and economic relief.

But analysts say North Korea will be unwilling to cede its nuclear deterrent unless it is given security guarantees that the US will not try to topple the regime.

Kim's comments seem to indicate he is hoping for a phased approach to solve the problem.

Lavrov warned against setting expectations too high, urging all sides to "avoid the temptation to demand everything and now," according to a transcript released by the Russian foreign ministry.