TOKYO — International Court of Justice judge Hisashi Owada is considering resigning from his post, a Japanese government source said Tuesday.

Owada, the 85-year-old father of Crown Princess Masako and a former president of the court, would quit before his second nine-year term ends in 2021 due partly to his age, the source said. He is not currently in charge of any case involving Japan as a main party.

The Japanese government is expected to nominate Yuji Iwasawa, a professor at the University of Tokyo’s Graduate Schools for Law and Politics, as the successor to Owada before elections at the U.N. Security Council and the General Assembly, the source said.

A former Japanese diplomat, Owada assumed senior posts such as vice foreign minister and ambassador to the United Nations before joining the 15-judge ICJ in 2003. He became the first Japanese to serve as president of the international court based in The Hague, the Netherlands, in 2009.

Owada remains a judge at the ICJ after leaving the presidential post in 2012.

Established in 1945, the principal judicial organ of the United Nations settles legal disputes between states and gives advisory opinions on legal questions referred to it by other U.N. organs.