The government presented three options Thursday for the country's new missile defense system, after it scrapped in June a plan to deploy Aegis Ashore land-based interceptors.
The options are building a destroyer vessel armed with the entire interceptor system including radars, deploying the system at a large-scale offshore facility similar to an oil rig or mounting the system on a private vessel such as a tanker.
The destroyer option does not exclude the construction of a conventional Aegis guided missile ship.
The possibility of the Ground Self-Defense Force taking charge of operating the offshore missile interception system instead of the Maritime Self-Defense Force, which is facing a crew member shortage, cannot be ruled out.
The alternative ideas were presented at relevant meetings held separately by the ruling Liberal Democratic Party and its coalition partner, Komeito.
The government is particularly interested in operating the Aegis Ashore system on a destroyer, coalition sources said.
"We plan to deploy (the interception system) on a mobile platform in the ocean, and we would like to look into the specifics with the United States and the suppliers in a prompt manner," Defense Minister Nobuo Kishi told the meeting.
However, none of the options have yet been fully technically validated. Furthermore, there are issues such as them being vulnerable to attacks and their costs being uncertain, people familiar with the matter said.
"We want to avoid being hasty. We will make considerations carefully," a ministry official said at a Komeito meeting, reflecting on the failure to deploy the previously planned Aegis Ashore system due to a lack of preparation.
The government hopes to select one of the three options by the time it compiles the fiscal 2021 budget late this year, after studying their technical aspects and calculating their costs with help of the private sector as well as the United States.
For that reason, the Defense Ministry will not present a specific cost estimate in its budget request at the end of this month.
At the meetings, participating lawmakers largely favored the destroyer construction idea as "technically reliable," while dismissing the option to use a private-sector vessel as "irresponsible."
Some participants called for the Aegis Ashore system to be deployed in locations other than the originally planned sites in Akita and Yamaguchi prefectures.
The ministry had also considered introducing an interception system that would detect an incoming missile with high-grade radar on land and shoot it down with missiles launched from a sea-based platform.
However, the ministry told the LDP that it had abandoned the option due to rising costs and technical problems, including an expected communication delay.