Prime Minister Shinzo Abe said the government "will step forward and implement all necessary policies" to deal with the flood of radioactive water from the plant, a legacy of the world's worst atomic disaster in 25 years.
The government will present a comprehensive package of measures on the water problem as soon as today, a senior official said.
Tokyo's measures come amid proposals to create a government agency devoted to decommissioning the Fukushima plant and as some outside the government call for a break-up of the operator, Tokyo Electric Power Co, or Tepco.
Two-and-a-half years after a massive earthquake and tsunami crippled the facility, the contaminated water is deteriorating, and the government is taking a more direct role as Tepco appears overwhelmed by the task.
Japan's Chief Cabinet Secretary Yoshihide Suga commented: "The government has stayed in the b ackground and extended support for the effort to tackle the problem of contaminated water.
"But we've now decided Tokyo Electric's patchwork response has reached its limit, and the government needs to come forward and quickly respond."