North Korean dictator Kim Jong-un's promise to suspend nuclear tests and missile launches immediately has triggered a warning from Australian Foreign Minister Julie Bishop that the declaration cannot be trusted unless the rogue state proves it is willing to abandon its weapons program.

The North Korean announcement marked a surprising shift in policy by Kim ahead of his meeting with South Korean President Moon Jae-in in two weeks and a historic summit with United States President Donald Trump planned for late May or early June.

“North Korea will have to make verifiable steps to show that it is genuine in abandoning its illegal nuclear weapons and ballistic missile testing and programs,” Ms Bishop said in London on Saturday.

“While we can cautiously note the statements, we need to see verifiable steps, because in the past North Korea has made promises and then failed to honour them.”