Japan's prime minister would usually meet key regional players for face-to-face talks at the Asia-Pacific Economic Cooperation summit, to be held in Vladivostok in eastern Russia.

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 Japan was considering suspending summits with South Korea "for the time being", including on the occasion of the APEC summit and an expected visit by the Japanese premier to South Korea as part of "shuttle diplomacy".

The foreign ministry official in charge of issues on the Korean peninsula told AFP the issue of a leaders' meeting was still under discussion.

"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 said.

However, 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."

Japan usually holds bilateral talks with key players on the sidelines of APEC including South Korea, but they are not usually announced until just before the meetings.

Lee said Monday his unprecedented visit to the islands was intended to press Tokyo to settle grievances left over from its colonial rule.

The visit Friday to the Seoul-controlled islands in the Sea of Japan (East Sea) infuriated Japan, which recalled its ambassador from Seoul.

It was the first trip by a South Korean president to the largely uninhabited volcanic outcrops.

Japanese Prime Minister Yoshihiko Noda called the visit "extremely deplorable", while Foreign Minister Koichiro Gemba told reporters Tokyo could ask the International Court of Justice to settle the row over ownership.

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. Presidential elections are due in December, although Lee cannot seek another term.

In March, Lee urged Japan to settle long-running grievances over wartime sex slavery, saying time was running out to resolve the issue.