South Korea warned North Korea yesterday there would be a price to pay if it launched a long-range missile, using its strongest language yet to try to dissuade Pyongyang from a test-flight.

US officials have said North Korea was preparing to test a long-range ballistic missile. Washington and Tokyo have warned Pyongyang of a harsh response if it went ahead with the launch.

“Whatever the nature of the launch object, it is wrong for North Korea to escalate tension this way,” South Korea’s chief presidential adviser on national security, Song Min-soon, said. Of course, if North Korea goes ahead with the launch, the government will take measures that will match the seriousness of that,” Song said in a commentary posted on the presidential Blue House Web site.

South Korea has previously said a missile test would pose a grave danger to regional security. Song did not say what measures Seoul might take, but South Korean officials have said they would be forced to reconsider fledgling economic ties with the impoverished North in the event of a missile launch.

Experts say North Korea is developing long-range missiles in order to one day deliver a nuclear weapon.