Japan's cabinet plans to approve an annual foreign policy report Friday that renews Tokyo's territorial claim to Seoul's easternmost islets of Dokdo, a diplomatic source said Thursday.

In a move certain to deepen diplomatic tension with South Korea, the Diplomatic Blue Book 2012 will reiterate claims that Dokdo is Japanese territory historically and under international law, the source said on condition of anonymity.

Dokdo, which lies closer to South Korea in the body of water that divides the Korean Peninsula and Japan, has long been a thorn in relations between the two countries. South Korea keeps a small police detachment on the islets, effectively controlling them.

South Korea rejects Japan's claim to Dokdo as nonsense because the country regained its independence from Japanese colonial rule and reclaimed sovereignty over its territories, including Dokdo and many other islands around the Korean Peninsula.

The latest move by Japan is expected to prompt heated reactions in South Korea and follows Tokyo's approval of school textbooks for high-school students last month that also reassert Japanese claim to Dokdo.

The Korean government has said it will firmly deal with the issue if Japan approves the diplomatic report laying claim to Dokdo.

Japan has sometimes omitted its claim to Dokdo from the diplomatic paper, as it did in 2002 and 2007, when the issue put a significant strain on ties with South Korea. (연합뉴스)