Russia and Japan have disputed ownership of the southern Kuril Islands, in Russia's Far East, for over 60 years. Japan maintains that their seizure was illegal, and the dispute has kept the two countries from signing a formal peace treaty following the end of WWII.
"The territorial issue has always been one of the most important for Japan as well as for Russia," Tomohiko Taniguchi, a deputy spokesman for the Japanese Foreign Ministry, said. "It [the issue] still remains topical for the upcoming summit meeting between [Russian] President Vladimir Putin and [Japan's] Prime Minister Shinzo Abe."
President Putin is set to meet with Japanese Prime Minister Abe on June 7 during the summit of the leaders of Group of Eight leading industrialized nations at Germany's Baltic resort of Heiligendamm from June 6 to 8.
Speaking at a news conference last Friday at the presidential residence near Moscow, President Vladimir Putin said Moscow did not believe the islands were up for discussion, but was willing to negotiate with Tokyo over the four islands.
"We don't consider them contestable, as the situation arose as a result of the Second World War, and was fixed in international law, and in international documents," Putin said. "But we understand the motivation of our Japanese partners. We want to get rid of all the thorns of the past, and we are seeking a solution to this issue together with Japan."
Putin also said that talks on the Kurils issue have moved away from rhetoric, and taken on a more businesslike character.
"We welcome this. And I would like to reiterate that even the Soviet Union demonstrated in their time a large degree of flexibility in resolving this issue, signing in 1956 a declaration according to which two of the islands would remain with the Soviet Union, and two would be passed to Japan," the president said.
The declaration was ratified by the Soviet Union's Supreme Council and by Tokyo, he said.
"But our Japanese partners suddenly, unexpectedly rejected this document, even though they had themselves ratified it. I'm sure you'll agree that under such conditions, it is not easy for us to reach a joint decision, but we are fully resolved to work on this together with [Japan]."
In the Treaty of San Francisco signed by Japan and the Allied Powers in 1951, which formally ended WWII, Japan renounced its rights to the Kuril Islands and Sakhalin. However, the four southern Kuril Islands were not specifically mentioned in the treaty, which was not signed by the Soviet Union.
Last year, Russia offered to return to Japan the Shikotan and Khabomai islands, with a combined area of just 276 square kilometers (172 square miles), or 6% of the disputed territory, on the condition that Tokyo renounce its claims to the two larger islands, Iturup and Kunashir, whose combined area totals 4,629 square kilometers (2,890 square miles). Japan rejected the proposal, claiming its right to all four islands.
Taniguchi reiterated that Tokyo is still interested in the mutually acceptable resolution, which would require some time to reach it adding that the issue should be viewed in a wide context of Russian-Japanese relations.
The high-ranking diplomat also said that Sunday's visit to the Kuril Islands made by Russian Foreign Minister Sergei Lavrov would not affect the agenda of the June 7 meeting between Putin and Abe.
On Monday Japan's Chief Cabinet Secretary Yasuhisa Shiozaki criticized Lavrov's visit to the Kuril Islands shortly before the G8 summit saying that in his opinion the visit may have a negative impact on Russian-Japanese negotiations on the territorial issue.
Lavrov was surprised by criticism from the Japanese official saying Tuesday: "I do not think I am prohibited from traveling across Russian territory. Moreover, I am surprised to hear this."
A source close to the Japanese government, who wished to remain anonymous, also confirmed that the territorial issue would be raised in Germany at the two leaders' meeting.
"There is no quick resolution, but Abe is interested to know what President Putin feels about this issue," the source said adding that in his opinion the territorial issue will not be the main issue for bilateral discussions.
"Believe it or not climate change is the most important issue for Japan," the source said. "Abe will ask President Putin to support his initiative 'Cool Earth 50' on the 50% reduction of greenhouse gas emissions by 2050."
He also said the leaders may discuss the current situation on the North Korean Peninsula and relations between Japan and North Korea.
As well as fears over North Korea's nuclear ambitions in Japan, which has maintained a firm anti-proliferation policy since the Second World War, the two countries have yet to resolve a dispute over the abduction by North Korea of 13 Japanese nationals in the 1970s and early 1980s, some of whose fate remains unknown. North Korean leader Kim Jong-il has admitted to the abductions.