The launch pad on the north-east coast has been picked up on satellite images
The first window in North Korea's five-day satellite launch plan has passed with no sign of a blast-off.
A South Korean expert said conditions in the launch area were not ideal, with "somewhat strong" winds and cloud.
Neighbouring states suspect the launch of the rocket is a cover for a long-range missile test and have urged North Korea not to go ahead.
North Korea has said the launch will happen between 4-8 April, during windows from 0200 to 0700 GMT.
Observers say North Korea is very likely to stick to this commitment, firing the rocket at the first sign of good weather during the given times.
Preparations for the satellite launch were complete and lift-off would take place "soon", North Korean state media had reported earlier on Saturday.
But conditions were "not ideal", with "somewhat strong winds" and partial cloud at the launch site in north-eastern North Korea, said a South Korean Meteorological Administration spokesman.
North Korea has said its rocket will pass over Japan. The first stage is expected to fall into the sea west of Japan, and the second stage dropping into the Pacific.
South Korea said it had convened a meeting of a special task-force, while security chiefs in Japan were said to be on stand-by. The US, Japan and South Korea have deployed warships with radar to seas off North Korea to monitor the launch.
Japan's government at one point said that North Korea was believed to have launched a rocket, but later retracted the statement saying the information was incorrect.
"We caused a great deal of trouble to the Japanese people," Defence Minister Yasukazu Hamada was quoted as saying by Reuters news agency.
"This was a mistake in the transmission of information by the Defence Ministry and the Self-Defence Forces. I want to apologise to the people from my heart."
"Preparations for launching Kwangmyongsong-2, an experimental communications satellite, by carrier rocket Unha-2 have been completed at the satellite launching ground in the east coastal area of the DPRK (North Korea)," KCNA said.
"The satellite will be launched soon," it added.
In recent days satellite images have shown activity at the Musudan-ri site and the rocket positioned upright on the launch pad.
North Korea says it is pursuing peaceful space development, but its neighbours believe it could be planning to test a new long-range weapon.
They suspect the launch is a cover for a test of the Taepodong-2 ballistic missile, which could put parts of the US within reach of the communist state.
Washington, Seoul and Tokyo have all criticised the launch plan, which would violate UN resolutions.
Earlier this week, US President Barack Obama and his South Korean counterpart Lee Myung-bak said a "stern, united response" would follow any rocket launch by North Korea.
Japan, meanwhile, has said it will shoot down the rocket if it misfires and endangers Japanese territory. It has sent two destroyers equipped with missile interceptor technology into the Sea of Japan (East Sea).
North Korea's military has threatened immediate retaliation if "even the slightest effort" is made to intercept its rocket.
The secretive country first test-fired a Taepodong-2 missile in July 2006. The missile failed shortly after launch and crashed into the sea.
Three months later it carried out a nuclear test. Talks between North Korea and five other nations - China, Russia, South Korean, the US and Japan - on an aid-for-disarmament deal are currently stalled.