Prime Minister Naoto Kan said on Friday that he would do everything in his power to ensure that Japan overcomes its worst crisis since World War II.

Speaking at a nationally televised news conference, Kan said that the fight to bring the nuclear crisis in Fukushima Prefecture under control would be a long one but he remained convinced that Japan would pull through.

"I am prepared for a long-term battle over the Fukushima nuclear plant and to win this battle," the prime minister said.

"We cannot say that the plant has been sufficiently stabilized, but we are preparing for all kinds of situations and I am convinced that the plant can be stabilized," he added.

Kan played down potential health risks caused by the radiation-leaking Fukushima Daiichi nuclear power plant, whose critical cooling systems failed after being pounded by a massive tsunami.

"As long as government advisories were adhered to, people's health wouldn't be compromised," he said. "In Japan, we ask people to follow the rules because if they do, there will be no damage to their health."

The prime minister also said that the government would decide whether to expand the evacuation zone from 20-km around the volatile facility based on advise from nuclear experts.

The International Atomic Energy Agency (IAEA) had urged Japan to widen the evacuation zone around the stricken plant and evacuate people out of the village of Iitate, 40 km northwest of the facility, on concerns of elevated levels of radiation found in air, soil and sea samples in the area.

But Kan said that evacuation advice from its own nuclear safety agency as well as global watchdogs was being heeded.

"Japan decides on the area of evacuation around the plant based on experts' advice and proposals," the prime minister said.

Kan's comments came despite the government's Nuclear and Industry safety Agency saying that radioactive water may be freely flowing into the Pacific Ocean through drainage systems and supply trenches.