Nippon Steel is also optimistic that demand growth will help it feed higher prices through to customers, Sakae said.

But Sakae is worried about coking coal prices that rose unexpectedly after output cuts on strikes and outages in Australia.

TEPCO vice-president Sakae Muto told journalists at the company's latest briefing that test results showing the plutonium came from samples taken a week ago.

The company's iron ore term contracts for April-June quarter are expected to come at around $77-78 a tonne, up from $57 this quarter, Sakae said.