The decision would mark the 25th delay for the plant in northern Japan, Kyodo said. Construction began in 1993.

A spokesman at JNFL declined to comment, but said its president, Naohiro Masuda, will hold a news conference about the plant later on Friday in Aomori.

The plant passed safety inspections by the country's nuclear watchdog, the Nuclear Regulation Authority (NRA), under the new regulatory standards in July. But JNFL figured the postponement was inevitable as it still needs to confirm detailed construction plans and implement safety measures, Kyodo said.

The plant is a key part of the country's nuclear fuel cycle, in which spent nuclear fuel is reprocessed into plutonium and then reused in reactors.

(Reporting by Yuka Obayashi; Editing by Tom Hogue)