US President Barack Obama on Thursday ordered a "comprehensive review" of nuclear power plants in the United States in light of the threat of a meltdown at Japanese nuclear reactors that were damaged in last week's massive earthquake, dpa reported.
The review comes as the United States began helping private citizens and the families of embassy and military personnel to leave north-eastern Japan, where workers continue battling to cool a number of damaged reactors at the stricken Fukushima power plant.
The US State Department in a travel warning earlier Thursday said it "strongly urges US citizens to defer travel to Japan at this time and those in Japan should consider departing." The first flight left Thursday and landed in Taiwan, carrying just under 100 Americans.
Speaking from the White House Rose Garden, Obama also said he remained "deeply concerned" about the crisis in Japan and said there was a "substantial risk" to residents near the Fukushima plant. He said the US was providing all the assistance it can to Japan.
The United States has called on US citizens within 80 kilometres of the power plant to evacuate - a far broader radius than the 20 kilometres recommended by Japanese authorities.
But the Pentagon said it would allow soldiers to move closer to the power plant if Japan requested their help. The US military has 14 US Navy ships and about 17,000 troops helping out with the relief effort.
Obama said Americans beyond the 80-kilometre radius were not yet at risk of radiation exposure, but said the US was helping people who wanted to leave for "prudent and cautionary measures."
While US nuclear power plants were designed to withstand major natural disasters, Obama also said the US had a "responsibility" to learn the lessons from the Japanese nuclear crisis.
Obama had therefore ordered the US nuclear regulator to conduct "a comprehensive review of the safety of our domestic nuclear plants in light of the disaster."
But Obama also sought to assuage the concerns of people in the United States who have feared that radiation from a meltdown of the Japanese plant could reach US shores.
"I want to be very clear. We do not expect harmful levels of radiation to reach the United States," Obama said.
Panicked Americans and people in other countries have rushed to buy potassium iodide tablets that can help protect them from radiation. But experts have warned that the tablets are unhealthy when taken under normal conditions.
Obama warned that US authorities "do not recommend that people in the United States take precautionary measures beyond staying informed."