Japan said on Wednesday it aims to decommission the tsunami-stricken Fukushima nuclear power plant over 30-40 years, as it unveiled the next phase in its cleanup plan for the complex.

After months of efforts Japan said last week that the Fukushima reactors were in a state of cold shutdown, when water cooling them is stable below boiling point, and that radiation at the plant's boundaries could now be kept at low levels.

Removal of spent fuel from the facility will begin within the next two years, the government said on Wednesday, with removal of fuel debris from the damaged reactors starting within 10 years.

The Fukushima Daiichi plant, 240 km (150 miles) northeast of Tokyo, was wrecked on March 11 by a huge earthquake and a towering tsunami which knocked out its cooling systems, triggering meltdowns, radiation leaks and mass evacuations.

The Japanese government plans to take a stake of more than two-thirds in Tepco in a de facto nationalisation of the utility, the Yomiuri newspaper said on Wednesday.

Trade Minister Yukio Edano said the total cost of the long-running cleanup was unclear but that plant operator Tokyo Electric Power Co Inc should shoulder in the financial burden.

It is difficult to estimate the cost of the plant clean up at this stage. That is why cost estimates were not included in the medium to long-term roadmap, Edano told a news conference.

We may at some point draw a clearer cost estimate but it would be difficult to make estimates of something four decades down the line in just one or two years from now.

(Reporting by Shinichi Saoshiro; Editing by Joseph Radford)