Japan will need up to 390,000 barrels a day of additional oil this year if the country keeps the 48 reactors currently offline idle for the rest of the year, the International Energy Agency said Friday in its monthly report.

The projection is 10,000 barrels a day higher than its previous estimate, the Paris-based energy watchdog said.

The Japanese power sector continues to confront significant summer power generation constraints, as only two nuclear reactors in western Japan are operating.

Reactivation of further idle capacity depends on a new nuclear watchdog being appointed in September, which will be responsible for authorizing nuclear plant start-ups.

Even if some more reactors are restarted, Japan will still need an additional 360,000 barrels a day, IEA said.

Japan's oil demand rose by 5.5% from a year earlier in June, after rising by an average of 10.7% in the previous five months.