The final line-up for the new cabinet is expected to be announced later Tuesday, but local media reported Abe was replacing Itsunori Onodera, defence minister since August 2017.

Onodera, seen as a defence expert, will reportedly be succeeded by Takeshi Iwaya, 61, a veteran politician who has had short stints in roles including vice minister for defence and foreign affairs.

The reshuffle follows Abe's reelection as leader of his Liberal Democratic Party last month, which puts him on track to become Japan's longest-serving prime minister in history.

Iwaya is expected to take over as Japan eyes the threat posed by North Korea despite easing tensions on the Korean peninsula and international negotiations on Pyongyang's denuclearisation.

In an annual defence review released in August, the defence ministry said North Korea continues to pose a "serious and imminent threat".

Japan's 2018 defence white paper also took aim at China's rise as a military power, saying Beijing was sparking "strong security concerns in the region and international community, including Japan".

Local media said Abe was expected to keep other key ministers in their posts, with chief cabinet secretary Yoshihide Suga, finance minister Taro Aso and foreign minister Taro Kono all staying on.