TOKYO - Japan will unveil on Monday details of "stress tests" idled nuclear power plants must undergo before they can be restarted, a senior official said on Sunday, as the government seeks to reassure the public over safety after the Fukushima disaster.

Gohsi Hosono, the minister appointed to oversee Japan's response to the crisis at the Fukushima nuclear power plant, told Fuji TV in an interview the government would also announce on Monday a plan for electricity supply over the next "one or two years" to allay businesses' fears over power shortages.

"The results of the new stress tests and the decision on restarts cannot be treated separately," Hosono said.

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He said the tests, intended to assess whether Japan's nuclear plants could withstand the kind of massive earthquake and tsunami that pushed Fukushima into crisis, would have different standards to those proposed by the European Union, adding: "This will be a Japanese-style test."  

In a sudden shift in policy, Prime Minister Naoto Kan said last week that Japan would administer stress tests for nuclear plants similar to those conducted by the European Union after the meltdowns at the Fukushima Daiichi nuclear plant.

The move was welcomed by critics who charge that Japan's current safety regulations have been too lax, but it also raised the prospect of power shortages that would stretch into the summer of 2012 and could cut into industrial production.

Japanese utilities are currently operating 19 of the 54 nuclear reactors that had been available before the March 11 earthquake and tsunami triggered meltdowns and explosions at four of the reactors at Fukushima Daiichi.

Japan's trade ministry said earlier this month that, without approval to restart reactors now down for maintenance, all of Japan's reactors could be shut by next April, adding more than $30 billion to the nation's energy costs.

The ministry had been pushing for a quick restart of the No 2 and No 3 reactors at Genkai in Kyushu as early as this summer.

The announcement of a new safety standard prompted a backlash from officials in communities near that Genkai plant who said they had been left in the dark about the shift in government policy.

The Fukushima nuclear plant lost power after the March 11 earthquake and tsunami. Three of the reactors had uranium fuel meltdown, and a series of hydrogen explosions scattered radioactive debris across a wide area.  

Some 80,000 people have been forced to evacuate the area around the plant because of the threat from radiation.

The area was hit by another strong quake on Sunday.