Japanese media are reporting Prime Minister Yoshihiko Noda has postponed a visit to Russia planned for next month citing President Vladimir Putin's health problems.
Kyodo and Jiji news agencies said Noda talked about the delay while meeting municipal officials during his trip to the northern island of Hokkaido on November 29.
The reports quoted an official as saying Noda mentioned "Putin's health problems."
The question of Putin's health has been the subject of intense media speculation recently.
Last week, Belarusian President Alyaksandr Lukashenka told Reuters that Putin had hurt his back practicing judo.
Putin's spokesman, Dmitry Peskov, has acknowledged Putin strained his back last month, but on November 30 dismissed reports of serious problems as "highly exaggerated."
Peskov says a visit by the Japanese prime minister could take place in January, 2013.
Based on reporting by Reuters, AFP, Interfax, and BBC Russian