TOKYO (Reuters) - Japan is leaning towards choosing the Aegis Ashore missile-defense system over another advanced system called Terminal High Altitude Area Defense (THAAD), government and ruling party sources said.

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Faced with North Korea’s rapid missile and nuclear development, and its threats, Japan has been looking into introducing a new missile-defense layer - either the THAAD or the Aegis Ashore, a land-based version of the Aegis system developed for war ships.

Lockheed Martin Corp makes both systems.

The government now favors the Aegis Ashore system as it comes with a wider coverage area, which would mean fewer units needed to protect Japan, and it is also cheaper, three government and two ruling party sources said.

The sources, who spoke this week, declined to be identified because they are not authorized to speak to media on the topic.

An Aegis Ashore unit costs about 70 billion-80 billion yen ($618 million-$706 million), while a THAAD unit costs more than 100 billion yen, the sources said.

Also, the introduction of Aegis Ashore would help reduce the burden of round-the-clock vigilance shouldered by Japanese warships equipped with the Aegis system, they said.

The government will make a final decision on the new system in coming months, after sending, possibly this month, an inspection team to Hawaii, where U.S. forces operate Aegis Ashore test facilities, they said.

Japan’s ruling Liberal Democratic Party in March urged Prime Minister Shinzo Abe’s government to consider acquiring the capability to hit enemy bases and to beef up missile defense.

($1 = 113.3300 yen)