Japan is preparing to ease antitrust rules that will enable some regional banks to merge as they struggle to stay profitable amid low interest rates and a declining population.

Prime Minister Shinzo Abe's government wants to allow such mergers to go ahead on a limited basis if the move prevents a regional bank from incurring big losses and if the newly formed bank ensures it will not unfairly raise lending rates.

Current rules block mergers between smaller banks outside of Japan's major cities if the newly formed bank will account for a dominant share of lending in the local community.

An advisory panel discussed the plan on Wednesday and will finalise the details so it can be included in the government's annual economic growth strategy expected sometime in June.