Japan was set to release its controversial diplomatic report on Tuesday that will likely contain Tokyo's repeated claim to South Korea's easternmost islets of Dokdo in what could be another setback in already-troubled bilateral ties, officials said.
  

Japan plans to publish its 2015 Diplomatic Bluebook later in the day, in which Tokyo is widely expected to intensify its territorial claim to a set of rocky islets in the East Sea.
  

In last year's report, Tokyo said the islets are "clearly an inherent territory of Japan," in light of historical facts and based upon international law.
  

The move comes just one day after Japan's education ministry irked South Koreans by unveiling the results of its regular review of textbooks for middle school students.
  

In 2011, only 4 out of 18 total textbooks contained Tokyo's claim that South Korea is illegally occupying Dokdo, where a small dispatch of Seoul's police are stationed as a token of its ownership.
  

This year, the number jumped to 13, representing the Shinzo Abe administration's attempt to bolster its efforts to lay claim to Dokdo.
  

Seoul's foreign ministry summoned Japanese Ambassador to Seoul Koro Bessho on Monday to deliver a message of protest.
  

Japan's continued provocation is expected to dampen the already strained bilateral ties between Seoul and Tokyo, experts say.
  

This year marks the 50th anniversary of normalizing their diplomatic relationship after Japan's brutal colonial rule of Korea from 1910-45.
  

Officials said that Japan may also change the expressions describing South Korea in its 2015 paper.
  

Last year's report said that Seoul and Tokyo are "the most important neighboring countries" to each other, adding that the two "share fundamental values such as freedom, democracy and the respect for basic human rights."
  

But this year, Japan is highly likely to delete the latter expression, according to officials.
  

Japan's foreign ministry also made a similar move by deleting that description from its webpage last month. The move is seen as expressing uneasiness toward Seoul following the recent indictment of a Japanese reporter from the Sankei Shimbun newspaper. (Yonhap)