The only remaining steps to go for the test would be setting up the launch pad and injecting solid fuel into a Taepodong-2 missile, said KBS, South Korea's largest television network, citing an unidentified high-level government official.
A Taepodong-2 missile is capable of reaching as far as the U.S. mainland with a light payload.
Foreign Ministry spokesman Choo Kyu-ho and other officials said they didn't have any such information.
But another government official, who requested not to be identified, said the Seoul government conveyed its concern to the North last month over a possible test, the AP reports.
Japanese and South Korean officials said last month the North had moved a missile to a launch site in a sign it was preparing a test launch. A senior South Korean intelligence official said it remained unclear whether the North was seeking to demonstrate its missile capability or was really preparing to fire a missile.