Work to remove melted fuel from the three crippled reactors at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear plant could start in 2020, the government and Tepco optimistically said Thursday, based on a revised, albeit vague, plan to decommission the stricken complex, a process expected to take decades.

The original melted-fuel extraction was expected to start in 2021, but the government, without elaborating, believes an improvement in work efficiency can move the date forward.

Tepco, however, said an exact start date currently is hard to forecast because the position and state of the fuel in reactors 1, 2 and 3, which suffered core meltdowns, remains unclear and all the utility can do at present is try, with makeshift equipment, to keep water circulating through the damaged containment vessels to prevent further massive radioactive fallout.