The rocket launch was originally scheduled to take place sometime between Dec. 10 and 22, South Korean Yonhap news agency reported.
However, the North's Korean Central News Agency said the launch will likely be postponed, giving few details on the situation.
An unnamed government official from Seoul with knowledge on the situation said the North is considering delaying the launch because of "technical problems," adding that "abnormal signs" were noticed since Saturday afternoon.
He didn't elaborate.
Observers said the North's decision to postpone shows that Pyongyang cares about the success of the rocket.
"North Korea's cautious stance on the rocket launch shows that it is not only focusing on just firing it off, but also caring about whether it can succeed," said Yang Moo-jin, a professor at Seoul's University of North Korean Studies. "The North seems to send a message that the rocket launch is not only for military purpose but also for its scientific technology."