The U.N. atomic energy chief called a Vienna summit to tackle mounting concerns about nuclear safety, saying on Monday the international community needed a coordinated response in the wake of Japan's crisis.
Japan is struggling to avert a severe meltdown at its Fukushima Daiichi nuclear power plant and officials said highly radioactive water had been leaking from the site hit by an earthquake and tsunami on March 11.
The disaster has prompted a rethink of nuclear power around the world, just as the technology was starting to regain momentum as a tool to fight global warming.
He said ministers from 151 IAEA member states should attend.
"(The) political level is needed, this is a very important issue, this is not only for experts or technical people," he told a news conference.
Amano said the Vienna conference would discuss the initial assessment of the Japanese accident and look at where things went wrong. It would also focus on boosting atomic safety and seek ways to improve nuclear crisis-management.
The IAEA has been criticised in the media and privately by diplomats for being too slow to react to the crisis.
The agency has said it can only communicate the data Japan gives it and says it lacks the power to enforce nuclear safety standards, something it may now lobby to change.
Amano described the situation at the site as "very serious."
"The difficult situation has not been overcome and it will take time to stabilise the reactors. Radioactivity in the environment, foodstuffs and water is a matter of concern in the vicinity of the Fukushima plant and beyond," he said.
IAEA officials said they were especially concerned about pools of radioactive water that have accumulated in the plant.
"This water in the turbines... is also for us maybe now the big concern," IAEA official Miroslav Lipar said.
The radiation appeared to be coming from damaged fuel that was escaping from containment vessels even though the reactor cores seemed largely intact, officials said.
"I think that from pressure readings our feeling is this is not a major breach of the reactor pressure vessel or the primary containment vessel, but we don't know that for certain," Amano deputy Graham Andrew said.
Two subcontractors hospitalised for radiation exposure after stepping into the pools were released on Monday, the IAEA said.
Andrew said weekend tests in six Japanese prefectures had detected radioactive iodine in asparagus, celery, cabbage, chives, cucumbers, eggplant, leeks, mushrooms, parsley, tomatoes, spinach and other leafy vegetables, strawberries and watermelon.
One sample of hana wasabi taken last week in Fukushima showed unacceptably high levels of iodine and caesium, he said.
Andrew said it was too early to draw conclusions about the impact of contaminated seawater on marine food.
Officials played down news that Fukushima's operator had found reactor-grade plutonium in soil at the plant.
"It means that there is degradation of the fuel, which is not news. We have been saying that consistently for so many days," IAEA safety chief Denis Flory told reporters.