The Japanese Defense Ministry wants to buy a Terminal High-Altitude Area Defense battery to step up its defense against North Korean missiles, NHK reported on Wednesday.

Until recently, there was speculation in Japan that Tokyo would deploy THAAD batteries only after 2018, when its five-year mid-term defense plan is complete.

But Tokyo decided to speed up efforts to bring in a THAAD battery because of the growing security threat in the wake of North Korea's recent frantic missile launches.

A North Korean Rodong missile fell into Japan's exclusive economic zone 250 km west of the Oga Peninsula in Akita Prefecture on Aug. 3.

The THAAD battery Japan is eyeing is the same interceptor type that Washington will deploy in South Korea.

This battery, which comes in with a radar and a missile launch pad, is aimed at intercepting incoming missiles during the terminal phase of their flight. But the Japanese military wants its own finger on the button rather than that of the U.S. forces as in South Korea.

The deployment could escalate a nascent arms race in East Asia. A diplomatic source said the deployment would deepen the trenches between the U.S., Japan and South Korea on one side and China, Russia and North Korea on the other, "even if the purpose is only defense against North Korean missiles."

Meanwhile, Vice Adm. James Syring, the chief of the U.S. Missile Defense Agency, is visiting South Korea on Thursday to discuss the THAAD deployment with the U.S. Forces Korea.