An advisory panel to the Japanese government says the reconstruction of towns and cities devastated by the March earthquake and tsunami could take a decade.
The panel says the first three years would be needed for tasks such as rebuilding roads and constructing temporary housing.
It says another four years may be necessary to rebuild towns, and it could take even longer to achieve full recovery.
Reuters quotes the panel as saying that the tragedy illustrates the shortcomings of centralised government and that greater regional autonomy is required.
The 11 March earthquake and tsunami left a large swathe of Japan's northeast in ruins, killed at least 13,000, forced about 130,000 peole into shelters and is estimated to have caused damage to the value of $US300 billion.
On Friday, Japan's cabinet approved almost $US50 billion in spending for post-earthquake rebuilding.