Japan's defence minister Tomomi Inada is this week expected to visit Guam and inspect the U.S. Terminal High Altitude Area Defense system, or THAAD.
Her visit to the US Andersen Air Force Base comes amid Japan's efforts to boost its ballistic missile defence system in response to North Korea's nuclear and missile programmes.
Japan has reportedly no concrete plan to introduce THAAD which aims to shoot down short, medium, and intermediate range ballistic missiles in their terminal phase.
Last July, South Korea announced it would deploy a battery of the THAAD system.
Its deployment is opposed by China and Russia.