One of six tsunami-crippled nuclear reactors appeared to stabilize on Saturday as Japan raced to restore power to the stricken power plant to cool it and prevent a greater catastrophe.
Engineers reported some rare success after fire trucks sprayed water for about three hours on reactor No.3, widely considered the most dangerous at the ravaged Fukushima Daiichi nuclear complex because of its use of highly toxic plutonium.
"The situation there is stabilizing somewhat," Chief Cabinet Secretary Yukio Edano told a news conference.
Engineers earlier attached a power cable to the outside of the mangled plant in a desperate attempt to get water pumps going that would cool overheating fuel rods and prevent a deadly radiation leak.
They hope electricity will flow by Sunday to four reactors in the complex about 240 km (150 miles) north of Tokyo.
Edano said radiation levels in milk from a Fukushima farm about 30 km (18 miles) from the plant, and spinach grown in Ibaraki, a neighboring prefecture, exceeded limits set by the government, the first known case of contamination since the March 11 earthquake and tsunami that touched off the crisis.
But he said these higher radiation levels still posed no risk to human health.
Prime Minister Naoto Kan, facing Japan's biggest disaster since World War Two, sounded out the opposition about forming a government of national unity to deal with a crisis that has left nearly 7,000 people confirmed killed and turned whole towns into waterlogged, debris-strewn wastelands.
Another 10,700 people are missing, many feared dead in the disaster, which has sent a shock through global financial markets, with major economies joining forces to calm the Japanese yen.
Officials connected a power cable to the No. 2 reactor and planned to test power in reactors No. 1, 2, 3 and 4 on Sunday.
Working inside a 20-km (12-mile) evacuation zone at Fukushima, nearly 300 engineers got a second diesel generator attached to reactor No. 6 working, the nuclear safety agency said. They used the power to restart cooling pumps on No. 5.
"TEPCO has connected the external transmission line with the receiving point of the plant and confirmed that electricity can be supplied," the plant's operator, Tokyo Electric Power Co, said in a statement.
Nearly 1.5 km (a mile) of cable is being laid before engineers try to crank up the coolers at reactor No.2, followed by numbers 1, 3 and 4 this weekend, company officials said.
"If they are successful in getting the cooling infrastructure up and running, that will be a significant step forward in establishing stability," said Eric Moore, a nuclear power expert at U.S.-based FocalPoint Consulting Group.
If that fails, one option is to bury the sprawling 40-year-old plant in sand and concrete to prevent a catastrophic radiation release. The method was used at the Chernobyl reactor in 1986, scene of the world's worst nuclear reactor disaster.
Underlining authorities' desperation, fire trucks sprayed water overnight in a crude tactic to cool reactor No.3, considered the most critical because of its use of mixed oxides, or mox, containing both uranium and highly toxic plutonium.
Japan has raised the severity rating of the nuclear crisis to level 5 from 4 on the seven-level INES international scale, putting it on a par with the Three Mile Island accident in Pennsylvania in 1979. Some experts say it is more serious.
Chernobyl, in Ukraine, was a 7 on that scale.
The operation to avert large-scale radiation has overshadowed the humanitarian crisis caused by the 9.0-magnitude quake and 10-meter (33-foot) tsunami.
Some 390,000 people, many elderly, are homeless, living in shelters in near-freezing temperatures in northeastern coastal areas.
Food, water, medicine and heating fuel are in short supply and a Worm Moon, when the full moon is closest to Earth, could bring floods to devastated areas.
"Everything is gone, including money," said Tsukasa Sato, a 74-year-old barber with a heart condition, as he warmed his hands in front of a stove at a shelter for the homeless.
Health officials and the U.N. atomic watchdog have said radiation levels in the capital Tokyo were not harmful. But the city has seen an exodus of tourists, expatriates and many Japanese, who fear a blast of radioactive material.
"I'm leaving because my parents are terrified. I personally think this will turn out to be the biggest paper tiger the world has ever seen," said Luke Ridley, 23, from London as he sat at Narita international airport using his laptop.
Officials asked people in the 20 km "take cover" zone to follow some directives when going outside: Drive, don't walk. Wear a mask. Wear long sleeves. Don't go out in the rain.
Though there has been alarm around the world, experts say dangerous levels of radiation are unlikely to spread to other nations.
The U.S. government said "minuscule" amounts of radiation were detected in California consistent with a release from Japan's damaged facility, but there were no levels of concern.
Amid their distress, Japanese took time to laud the 279 nuclear plant workers toiling in the nuclear plant's wreckage, wearing masks, goggles and protective suits sealed by duct tape.
"My eyes well with tears at the thought of the work they are doing," Kazuya Aoki, a safety official at Japan's Nuclear and Industrial Safety Agency, told Reuters.
G7 Intervention for Yen
The Group of Seven rich nations succeeded in calming global financial markets in a rare concerted intervention to restrain a soaring yen - the first such joint intervention since the group came to the aid of the newly launched euro in 2000.
Japan's Nikkei share index recovered some lost ground by the end of a week which wiped $350 billion off market capitalization.
The government plans to provide up to 10 trillion yen ($127 billion) in cheap loans to help businesses get back on their feet. The plight of the homeless worsened following a cold snap that brought heavy snow to the worst-affected areas, the Nikkei daily reported.
But the immediate problems remained huge for many people. Nearly 290,000 households in the north still have no electricity and about 940,000 lack running water.
Aid groups say most victims are getting help, but there are pockets of acute suffering.
"We've seen children suffering with the cold, and lacking really basic items like food and clean water," Stephen McDonald of Save the Children said in a statement.