U.S. officials are alarmed at how the Japanese are handling the escalating nuclear reactor crisis and fear that if they do not get control of the plants within the next 24 to 48 hours they could have a situation that will be "deadly for decades."
"It would be hard to describe how alarming this is right now," one U.S. official told ABC News.
President Obama has been briefed by nuclear experts.
The Japanese have evacuated most of the reactor personnel from the Fukushima nuclear complex and are rotating teams of 50 workers through the facility in an attempt to cool it down.
"We are all-out urging the Japanese to get more people back in there to do emergency operation there, that the next 24 to 48 hours are critical," the official said. "Urgent efforts are needed on the part of the Japanese to restore emergency operations to cool" down the reactors' rods before they trigger a meltdown.
"They need to stop pulling out people—and step up with getting them back in the reactor to cool it. There is a recognition this is a suicide mission," the official said.
The official said the United States is in very deep consultations with Japanese about the way forward and that the only thing that has been favorable is the wind pattern that is blowing the contaminated material out to sea instead south towards Tokyo and other populated areas, but that can't be counted upon.
The U.S. official says experts believe there is a rupture in two, maybe three of the six reactors at the Fukushima power plant, but as worrisome is the fact that spent fuel rods are now exposed to the air, which means that substances like cesium, which have a long half-life, could become airborne.
"That could be deadly for decades," the official said.
There is a growing concern around the world that a nuclear catastrophic disaster is in the works.
"There is talk of an apocalypse and I think the word is particularly well chosen," European Union's energy commissioner Günther Oettinger said today, according to various reports. "Practically everything is out of control. I cannot exclude the worst in the hours and days to come."
The United States has instituted a 50-mile evacuation zone for U.S. forces and American citizens from the Fukushima power plant, four times the size of Japan's 12-mile evacuation zone. Only exceptions that are made are for relief missions.
"Recently the NRC made a recommendation that based on the available information that we have, that for a comparable situation in the United States, we would recommend an evacuation to a much larger radius than has currently been provided in Japan," Nuclear Regulatory Commission Chairman Greg Jaczko said at a hearing of the House Energy and Commerce Subcommittee.
Jaczko said of the four plants that are endangered at the Fukushima site, there has been a hydrogen explosion at one unit and secondary containment has been destroyed.
"We believe radiation levels are extremely high, which could possibly impact ability to take corrective measures," he said.
U.S. analysis show that some of the radiation from the Fukushima nuclear power plant has drifted northward and out to sea, officials say, but the country is hardly clear of danger.
U.S. Fears Japan's Crisis Could Be Worse Than Chernobyl
Thousands of people flocked to Tokyo's Narita Airport today amid rising concerns of a radioactive fallout.
The head of the U.S. Department of Energy said today that the nuclear disaster unfolding in Japan could be worse than the 1979 Three Mile Island accident in Pennsylvania that dampened Americans' view of nuclear power plants for decades to come.
"Events unfolding in the Japan incidents appear to be more serious than Three Mile Island. To what extent, we don't know that. They are unfolding hour by hour," Energy Secretary Steven Chu said earlier today at the hearing.
Chu's assessment is in line with views expressed by many experts, some of whom even believe the Japan crisis could be worse than the 1986 Chernobyl nuclear disaster in Ukraine that left hundreds sick and killed several from radiation.
The United States has deployed thousands of military and civilian staff to assist the Japanese in dealing with the aftermath of the earthquake and the resulting tsunami, which has killed thousands.
To date there have been 113 helicopter missions and 125 fixed wing missions. More than 129,000 pounds of water and 4,200 pounds of food have been delivered .
The Department of Energy and Nuclear Regulatory Commission has sent teams of U.S. experts to assess the nuclear situation.
U.S. aid to Japan has reached nearly $5.9 million, with total planned assistance amounting to $8 million. USAID says the primary humanitarian needs on the ground remain food, safe drinking water, blankets, medical supplies, fuel, and sanitation infrastructure.
ABC News' Huma Khan and Luis Martinez contributed to this report.