The foreign ministers of Japan and Russia have failed to narrow their differences over four Russian-held islands claimed by Japan. But they agreed to continue negotiations.Taro Kono and Sergey Lavrov met for about 90 minutes on Saturday in Munich, Germany, on the sidelines of a security conference. The ministers are in charge of negotiations on concluding a peace treaty that would include a solution to the islands issue. Kono said at the start of the meeting that he wants to have thorough discussions based on the agreement reached between Japanese Prime Minister Shinzo Abe and Russian President Vladimir Putin in November.