Officials said Thursday that the nation's industrial output has fallen by half in the past two months.
"The main problem now is not to raise industrial output but to save people from freezing to death," said Deputy Prime Minister Anatoly Dyuba.
Ukraine imports almost two-thirds of the energy it needs, buying oil, natural gas and coal from Russia, Turkmenistan and Poland.
"We don't have money either to buy fuel or to pay salaries to (energy sector) workers," Dyuba said.
Energy officials have imposed strict conservation measures.
Beginning this week, hot water was supplied to apartments in Kiev, the capital, for only three hours a day. Television broadcasts were cut to seven hours a day. Street lights and illuminated billboards have been turned off.
Energy officials will also cut the power to entire cities for several hours a day to save electricity.
On Wednesday, some 800,000 people in three areas of Kharkiv, Ukraine's second largest city, were without electricity for three hours.
Energy Minister Vilen Semenyuk said Ukraine's power grid has been so overpressed by energy-hungry consumers that he feared the automatic switch-off to the nuclear-power industry might be triggered.
This nation of 52 million people gets 40 percent of its energy from nuclear power.
Ukraine is among the world's largest producers of steel, rolled metal and chemical products, which are its main sources of hard currency. But most of its plants can't pay for the energy they use.
"Most of Ukraine's chemical and metallurgical plants stand idle because of the energy shortage," said Dyuba.
"Machine-building plants alone owe some 25 trillion karbovantsy ($250 million) for fuel. We have stopped supplying energy to the worst debtors," he said.
At the huge Dneprodzerhinsk steel plant, only two of the 16 blast furnaces were operating. Only one of the six huge rolling mills at the Krivorozhstal steel plant was working.
"We've stopped about one-third of Ukraine's industrial plants, without any immediate hope of restarting them," Igor Stukalenko, head of the fuel department at the Ministry of Machine-building.
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