Japan's Yukiya Amano is set to be re-elected unopposed as head of the U.N. nuclear watchdog, a diplomatic source said Tuesday.

With no opposition apparently being voiced against his re-election, the 69-year-old Japanese is expected to stay on as the director-general of the International Atomic Energy Agency for another four years from December, subject to approval by the IAEA board of governors in March and a general assembly meeting in September.

A former Japanese diplomat, Amano will be tackling issues such as nuclear nonproliferation, including North Korea, which has been conducting nuclear tests in defiance of the international community. He has also been keen to strengthen the IAEA's engagement in overseeing Iran's nuclear agreement with global powers.

Amano has also been promoting vigilance regarding the safety of atomic power stations and oversaw the compilation of a report on the Fukushima nuclear crisis.

Candidacy filings for the election process closed Saturday.

Amano first assumed the post of IAEA director-general in December 2009 and is currently in his second term.