Japan's Prime Minister Naoto Kan says the nuclear crisis at the crippled Fukushima plant is "very grave."
Kan said on Friday the police, fire department and military were "putting their lives on the line" to cool the highly radioactive fuel rods at the complex.
Officials on Friday raised the severity rating of its nuclear disaster from 4 to 5 on a 7-point international nuclear event scale.
Firefighters were dousing water on damaged reactor buildings with powerful hoses. But they have to limit their time inside the complex due to the high radiation levels.
Japanese engineers also are extending an emergency power cable to the nuclear reactor complex. A steady supply of power could enable workers at the Fukushima plant to get water pumps working again.
Kan tried to reassure his nation, saying Friday that he expected that in the "not so distant future" the overall situation will be controlled.
The head of the International Atomic Energy Agency, Yukiya Amano, says Japan is racing against time to cool the overheating reactors. Amano arrived in Japan Friday to meet with top Japanese officials and learn how the IAEA can help with the crisis.
The increase in the nuclear accident's severity rating comes shortly after the chief secretary of Japan's cabinet, Yukio Edano, tried to calm fears about the radiation. He said elevated radiation levels detected kilometers away from the plant were not a health risk.
The International Atomic Energy Agency says that Japanese authorities have told them they have successfully laid a cable line to reactor number two at the nuclear plant. However, it is not clear how close workers are to actually restoring power.
The VOA correspondent in Japan's Fukushima Prefecture says government officials are not expecting power to be re-connected to reactors number two and three until Sunday.
The cooling problem is particularly critical at the number three nuclear reactor, where the risk of an increased level of radioactive leaks is considered especially high.
The risk of radiation poisoning has already forced the evacuation of more than 200,000 people who lived within 20 kilometers of the reactor site. Many are in makeshift shelters, with inadequate food, water and other supplies, in frigid winter weather.
For anyone still living inside a wider radius from the plant - 30 kilometers - Japanese authorities said everyone should remain indoors and take measures to minimize the amount of outside air entering their living quarters.
Three of the Fukushima plant's six reactors were operating when the quake struck, while three others were shut down for maintenance. Explosions have rocked the three units that had been in operation, causing varying degrees of damage.
Some information for this report was provided by AP, AFP and Reuters.