The Diet enacted a law Friday for upgrading key ports across Japan to attract more tourists on cruise ships under joint efforts by the public and private sectors.

The amendment of the existing port law allows cruise ship operators to use piers on a priority basis in exchange for their building or renewing terminal buildings at designated ports.

The state and municipalities, on their part, will shoulder the burden of introducing piers that are exclusively prepared for large cruise ships.

The Land, Infrastructure, Transport and Tourism Ministry will designate six ports, including Yokohama, as targeted international cruise ship hubs and consider making additions to the list in the future.

The five other ports are Shimizu in Shizuoka Prefecture, Sasebo in Nagasaki Prefecture, Yatsushiro in Kumamoto Prefecture, and Motobu and Hirara in Okinawa Prefecture.

The maintenance plan for the ports shows cruise ship operators there would construct or renovate terminal buildings that house souvenir shops and tourist counters while being given priority in using the special pier for cruise ships for 15 to 20 years.

Given that the big earthquake last year in Kumamoto disrupted port services, the ministry will also introduce an emergency system under which the state would take over port control at the request of municipalities hit by disasters.

Japanese ports have been major gateways for tourists from the rest of Asia, bringing nearly 2 million visitors in 2016, a sharp increase from 1.1 million the year before.

The number overall set a record of 24.04 million in 2016, up 22 percent from the previous year and over 20 million for the first time, according to the ministry.

To attract 40 million tourists in 2020, when Japan hosts the Tokyo Olympics, the government is planning to upgrade airports and seaports, as well as improve access to national parks and cultural attractions.