Japan's communications ministry plans to require key mobile phone base stations to have at least 24 hours of backup power.
The move comes after a series of powerful typhoons caused prolonged disruption to mobile communications last year.
Telecom firms are already required to install backup power sources at facilities that relay mobile phone signals. But the rules do not specify how long the emergency supply should last.
Officials plan to mandate base stations that cover local government offices have at least 24 hours of backup power through generators or batteries.
A non-binding target of 72 hours is planned for areas with prefectural government offices. It will also apply to base stations covering municipal offices in remote islands and mountain regions, where post-disaster recovery takes more time.
Officials say that about 5 percent of the roughly 1,800 local government offices in Japan are in areas with base stations that lack 24-hour backup power.
The communications ministry plans to draft revised rules by the end of June.