North Korea says it has completed its first military surveillance satellite and leader Kim Jong Un has approved final preparations for the launch.
"We will take destructive measures against ballistic and other missiles that are confirmed to land in our territory," Japan's defence ministry said in a statement, Reuters reported.
The ministry said it would use its Standard Missile-3 (SM-3) or Patriot Missile PAC-3 to destroy a North Korean missile.
Japanese Prime Minister Fumio Kishida told reporters that any North Korean missile launch would be a serious violation of UN Security Council resolutions.
"We strongly urge North Korea to refrain from launching," his office said in a post on Twitter, adding it would cooperate with its U.S. ally, South Korea and other countries, and would do all it could to collect and analyse information from any launch.
South Korea joined Japan in calling for North Korea to scrap the planned satellite launch.
North Korea has conducted a series of missile launches and weapons tests in recent months, including a new, solid-fuel intercontinental ballistic missile.