Prime Minister Shinzo Abe is expected to order his government later in the day to hand over public money to help foot the bill for ramped-up measures, the first time that Tokyo has committed extra funds to deal with the growing problem.
"Taking measures to contain contaminated water is an important part of the process towards decommissioning (the site)," Chief Cabinet Secretary Yoshihide Suga, the government's top spokesman, told reporters.
In May, Tokyo ordered plant operator Tokyo Electric Power (TEPCO) to build new barriers around the plant's reactors to contain toxic water that is used to keep the reactors cool, a measure that could cost up to USD 410 million.
There have been growing fears that existing safeguards will soon be overwhelmed by the highly radioactive water.
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"As this large-scale construction of walls is unprecedented in the world, we think the government should take a step forward and support the plan," Suga said.
Suga's comments come after Fukushima operator TEPCO last month admitted for the first time that radioactive groundwater had already leaked outside the nuclear plant, confirming long-held suspicions of ocean contamination from the shattered reactors.
The leaks have triggered alarm bells over the plant's precarious state and TEPCO's ability to deal with a long list of problems two years after it was swamped by a tsunami, sending reactors into meltdown. The company has faced widespread criticism over its lack of transparency in making critical information public.