Story highlights The US military will test-fire an improved Standard Missile off a Navy ship

The program has been in development with Japan

(CNN) The Pentagon will conduct two major high-stakes tests in May of its ability to shoot down missiles launched out of North Korea.

The long-scheduled tests in the Pacific are part of the US military's overall ballistic missile defense program to defend against North Korean or Iranian threats -- but are, for now at least, aimed at ensuring the US can defend against a threat from North Korea, US defense officials said.

One of the actions will involve test-firing an improved Standard Missile off a Navy ship, a defense official said. The tests are taking place over the Pacific because that's where the test ranges are large enough to accommodate them.

The upgraded missile has only been tested once before . The new version has an improved booster and warhead. That means the missile could fire at longer ranges, presumably farther from the North Korean coastline, and have a greater chance of hitting the threatening incoming missile.

The program has been in development with Japan and is aimed at shooting down intermediate-range North Korean missiles that pose a threat to the US ally.

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