Citing unidentified people at the Imperial Household Agency, NHK said it learnt that the emperor told close aides that he wants to pass the throne to the Crown Prince.
"Sources say that he wants to step down before he is too frail to carry out his duties fully," NHK said.
Sources say the Imperial Household agency is planning an occasion for the emperor to address the public, it added.
The emperor, 82, has reigned for 28 years. He would be succeeded by his eldest son, Crown Prince Naruhito.
Emperor Kokaku, who gave up the throne in 1817, was the last emperor to abdicate, NHK said.
Akihito succeeded his father, Emperor Hirohito, who was once worshipped as a living demigod and served as Japan's commander-in-chief during its march across Asia in the 1930s and 1940s. The Japanese throne is held in deep respect by much of the public, despite being largely stripped of its mystique and quasi-divine status in the aftermath of the war.
The emperor had a heart surgery in 2012. He was treated in 2003 for prostate cancer.
In an AFP report dated November 15, 2013, the Imperial Household Agency said the emperor opted to be cremated like most ordinary citizens in the densely populated nation. That would mark the first time in almost 400 years that a Japanese emperor has not been buried.