Preparations for launch were nearing completion but technicians were thinking of delaying it, the Korean Central News Agency said, citing the Committee for Space Technology.
The reasons for the delay were not clear.
The Stalinist state originally said it would launch the rocket between December 10 and 22.
North Korea said the rocket would transport a satellite into space.
The United States, South Korea, Japan and other countries suspect the launch is to test technology for an intercontinental rocket. Such a rocket could carry an atomic warhead.
North Korea's most recent launch of a long-range rocket, which it said would put a satellite into orbit, failed in April when it broke apart shortly after takeoff.
The United Nations Security Council condemned the launch.//DPA