The leaders of Japan and Russia hold crunch summit talks on Tuesday, with the two countries locked in an undiplomatic war of words over a set of disputed islands. Simmering tension between Moscow and Tokyo over the islands has ramped up in recent weeks, with Russia angrily accusing Japan of whipping up tension ahead of the summit and failing to accept it lost World War II. Setting the tone for the talks, Putin's foreign policy advisor Yuri Ushakov admitted the meeting would "not be easy."

The Russian army claimed the four islands in the closing days of World War II and a dispute over their sovereignty prevented the two countries signing a peace treaty -- a situation both countries have vowed to rectify.