The launch would be a "violation of U.N. Security Council resolutions. We are urging North Korea to exercise restraint as what it is going to do will undermine regional stability," Kawamura told a news conference.

North Korea warned Monday that any move to intercept what it calls a satellite launch would result in a counterstrike against the countries, such as Japan, the United States and South Korea, trying to stop it.

Kawamura stressed that Japan's Defense Ministry and Self-Defense Forces have a responsibility to protect the country's security and it is constantly collecting information and making preparations, although he did not say they are especially tightening their security at this time.

North Korea said earlier it is preparing to put a communications satellite into space, but outside observers suspect it may in fact be a test-firing of a long-range ballistic missile.

Japan, South Korea and the United States have said that even if Pyongyang launches a satellite, it would violate existing U.N. Security Council resolutions.