Japan is likely to make a significant upgrade to its Patriot missile defence system in time for the 2020 Tokyo Olympic Games and to be able to intercept more advanced North Korean ballistic missiles in future.
The Missile Segment Enhancement could double the range of the current Patriot Advanced Capability-3 (PAC-3) missiles to around 30 km (19 miles), sources aware of the plan told Reuters news agency. The upgrade is expected to start next year.
"The upgraded PAC-3 is necessary to counter the Musudan," said one source, referring to Pyongyang's intermediate-range ballistic missile.
However, a spokesman for Japan's Defence Ministry said "nothing has been decided" on the PAC-3 upgrade.
The International Olympic Committee's decision to grant Tokyo the 2020 games will help unlock funding for the PAC-3 upgrade despite military budget constraints, the sources told Reuters.
Around 100 billion yen ($955 million) in funding would be requested in the next defense budget proposal for the year starting April 2017, one of the sources said.
Japan is also considering purchasing the advanced Terminal High Altitude Area Defense, or THAAD, anti-missile system, which Washington and Seoul agreed to deploy in South Korea earlier this month.
The Patriot upgrade would likely be an enhancement to Japan's ballistic missile defense, rather than an alternative to THAAD or a similar system.