Japan may halt summit meetings with South Korea, a report said Tuesday, as a diplomatic spat between the neighbours worsened and Seoul called on the Japanese emperor to apologise for past atrocities.
A proposed visit to a controversial Tokyo war shrine by two Japanese cabinet ministers, for the first time in several years, was also rubbing salt into decades-old wounds, with Seoul urging the men to stay away.
Japan's prime minister would usually meet key regional players for face-to-face talks at the Asia-Pacific Economic Cooperation (APEC) summit, to be held in Vladivostok, eastern Russia, next month.
But Tokyo is scrabbling to find a suitable response to a visit last week by South Korean President Lee Myung-Bak to islands known in Japan as Takeshima and in Korean as Dokdo, which are claimed by both sides.
Japan's conservative Sankei Shimbun daily said Tokyo was considering suspending summits with South Korea "for the time being", including at APEC and a trip by the Japanese premier to South Korea as part of "shuttle diplomacy".
The Tokyo foreign ministry official in charge of issues on the Korean peninsula told AFP: "If we didn't set a bilateral summit with South Korea on the sidelines of APEC, it doesn't mean a 'cancellation' because it was never officially planned."
He added: "There is an opinion (in the government) that Japan should tell President Lee our opinion face-to-face, so I don't know if a summit will take place at this point or not."
Lee's trip to the islands in the Sea of Japan (East Sea) provoked a furious response, with Tokyo recalling its ambassador from Seoul.
The visit, which Japanese Premier Yoshihiko Noda dubbed "extremely deplorable", was the first by a South Korean president to the largely uninhabited volcanic outcrops.
South Korea on Tuesday said two Japanese cabinet ministers who have announced their intention to go to the Yasukuni shrine, a spot that honours Japan's war dead, should stay away.
"The (Seoul) government holds strongly to a position that Japanese authorities including cabinet ministers must not pay respects at the Yasukuni shrine," said Seoul foreign ministry spokesman Cho Tai-Young.
"We again strongly urge the Japanese persons concerned not to commit such acts."
The two ministers have said they plan to visit the shrine Wednesday, the anniversary of Japan's World War II surrender.
South Korea marks the date as Liberation Day, the anniversary of the end of Japan's harsh colonial rule over Korea from 1910 to 1945.
President Lee meanwhile ramped up his anti-Japan rhetoric, saying Emperor Akihito would have to sincerely apologise for past excesses should he wish to go to South Korea.
"If (Japan's emperor) wishes to visit South Korea, I wish he would visit and sincerely apologise for those who passed away while fighting for independence," the South Korean leader said during a meeting with teachers.
"If he is going to visit with a term such as 'regret', there would be no need for him to come," Lee said, according to a report on the presidential website.
It was unclear if there had been any recent discussions about such a visit by the emperor.
Japan has been working to improve ties with South Korea and had previously seen Lee as a pragmatic politician who could talk about the future of the two countries without getting hung up on the bitter legacy of the past.
But ties have taken a dramatic turn for the worse in recent months.
In June, Lee's administration had been set to sign a landmark agreement to share sensitive information with Japan, in what would have been the first military accord between the two countries since 1945.
But South Korea postponed the signing at the last minute, with both the ruling party and opposition parties concerned about public opposition.