North Korean leader Kim Jong Un's powerful sister said Monday that Japanese Prime Minister Fumio Kishida has requested a summit with her brother, adding any meeting was unlikely without a policy shift by Tokyo.

"Kishida recently conveyed his wish to meet with the Chairman of the State Affairs Commission of the Democratic People's Republic of Korea at the earliest date possible," Kim Yo Jong said in a statement carried by the official Korean Central News Agency.

Relations between the two countries have long been dogged by issues including compensation for Japan's brutal occupation of the Korean peninsula between 1910 and 1945 and more recently by Pyongyang's firing of missiles over Japanese territory.

The abduction by North Korean agents of Japanese citizens in the 1970s and 1980s -- forced to train spies in Japanese language and customs -- has also long been a major point of contention.

Kishida has said he wants to change the relationship between Tokyo and Pyongyang and last year expressed his wish to meet with North Korea's leader "without any conditions", saying in a speech at the UN General Assembly that Tokyo was willing to resolve all issues, including the kidnappings.

Last month, the North's Kim Yo Jong -- who is one of the regime's key spokespeople -- hinted at a possible future invitation for the Japanese leader to visit North Korea.

She said on Monday that it was "Japan's political decision that matters the most to pave a new charter in North Korea-Japan relationship."

Kidnapping issue

"If Japan tries to interfere with our exercise of sovereign rights like it does now and is resolutely preoccupied with the kidnapping issue, which we have no way of solving or knowing about, it will inevitably face the reputation that the Prime Minister's plan is nothing more than aimed at drawing popularity," she said.

North Korea admitted in 2002 that it had sent agents to kidnap 13 Japanese people in the 1970s and '80s who were used to train spies in Japanese language and customs.

The abductions remain a potent and emotional issue in Japan and suspicions persist that many more were abducted than have been officially recognised.

Analysts have long said that contention over the issue could hinder progress towards a summit between Kishida and Kim Jong Un.

Kim Yo Jong said that Kishida "must know that he cannot meet our leadership just because he wants or has decided to or that we will grant him such a meeting just because." 

"If Japan sincerely wants to improve the relationship between the two and become our close neighbour to contribute to guarantee peace and stability in the region, it needs to have political courage to make strategic choices befitting to its national interests," she said.

Japan's former prime minister Junichiro Koizumi paid a landmark visit to Pyongyang while in office in 2002, meeting Kim's father Kim Jong Il and setting out a path to normalise relations in which Japan would offer economic assistance.

The trip led to the return of five Japanese nationals and a follow-up trip by Koizumi, but the diplomacy soon broke down, in part over Tokyo's concern that North Korea was not coming clean about the abduction victims.