WASHINGTON (AP) - President Barack Obama, trying to reassure a worried nation, declared Thursday that "harmful levels" of radiation from the Japanese nuclear disaster are not expected to reach the U.S., even as other officials conceded it could take weeks to bring the crippled nuclear complex under control.
The situation remains dangerous and complicated at the damaged Fukushima Dai-ichi reactors in northeastern Japan, U.S. officials said.
"We've seen an earthquake and tsunami render an unimaginable toll of death and destruction on one of our closest friends and allies in the world," Obama said in brief remarks at the White House after a visit to the Japanese Embassy to offer his condolences.
Obama said he had asked the Nuclear Regulatory Commission to conduct a "comprehensive review" of the safety of all U.S. nuclear plants.
"When we see a crisis like the one in Japan, we have a responsibility to learn from this event and to draw from those lessons to ensure the safety and security of our people," Obama said.
There are 104 nuclear reactors in the United States, providing roughly 20 percent of the nation's electricity. "Nuclear energy is an important part of our own energy future," Obama said.
Meanwhile, the first evacuation flight of U.S. citizens left Japan, the State Department said.
In the U.S., Customs and Border Protection said there had been reports of radiation being detected from some cargo arriving from Japan at several airports, including ones in Chicago, Dallas and Seattle.
Radiation had not been detected in passengers or luggage. And none of the reported incidents involved harmful amounts.
Homeland Security Secretary Janet Napolitano said the agency was screening passengers and cargo for "even a blip of radiation."
Obama said he knows that Americans are worried about potential risks from airborne radiation that could drift across the Pacific. "So I want to be very clear," he said. "We do not expect harmful levels of radiation to reach the United States, whether it's the West Coast, Hawaii, Alaska or U.S. territories."
At his visit to the Japanese Embassy, Obama signed a condolence book and said: "We feel a great urgency to provide assistance to those ... who are suffering."
In the book he wrote, "My heart goes out to the people of Japan during this enormous tragedy. Please know that America will always stand by one of its greatest allies during this time of need."
"Because of the strength and wisdom of its people, we know that Japan will recover, and indeed will emerge stronger than ever," he wrote.