Russia's Gazprom PJSC isn't confident in Japan's future as a growing natural gas user, which may damp prospects of a proposed pipeline between the countries as Premier Shinzo Abe travels to Moscow later this month.

"The demand situation in Japan is not clear yet for the next 15, 20, 25 years," said Alexander Medvedev, deputy head of the Kremlin-backed exporter. The country's nuclear reactor restarts, use of coal and rising energy efficiency are making the outlook for gas uncertain, he said in an interview at the Gastech conference in Chiba, Japan. The world's biggest exporter sees brighter prospects in China.

Abe, seeking to deepen economic ties with Russia in an effort to resolve a 70-year-old dispute over islands off Hokkaido, is set to visit Moscow on April 27. Russian gas supplies to Japan, including the possible pipeline between the nations, could be discussed during the visit, Russia's Kommersant newspaper reported last month.