"We hope the launch will go ahead as scheduled this time."
Fuel injection will start two hours before the launch and the engines will be ignited 3.8 seconds before lift-off.
The first seconds will be crucial as the main engine pushes the 140-tonne rocket off the launch pad.
"If there is a sudden gust of strong wind or any other slight problem in the stabilisation mechanism, the rocket can tip over and be lost," Min Kyung-Ju, head of the Naro Space Centre, told South Korea's Yonhap news agency.
The second attempt, if successful, will put a South Korean satellite into orbit, operated in partnership with Russia. The project has been delayed seven times since 2002.
A successful launch would make South Korea only the 10th nation in the world to send its own communications satellite into orbit from its own soil.
Although the rocket's first stage was Russian-made, South Korean experts said they had gained valuable know-how that could enable them to build their own launch vehicle by 2018.
Rival North Korea, bristling from a UN censure for launching a long-range rocket in April, has warned it would be "watching closely" for the international response to the South Korean launch.
|North Korea says it will watch the world's reaction to Seoul's rocket launch [AFP]
North Korea launched its own three-stage rocket on April 5 claiming it sent a communications satellite into orbit, but there were doubts the mission succeeded.
The United States, Japan and others have called Pyongyang's rocket launch a cover for test of long-range missile technology.
The UN Security Council also condemned the launch, saying it was a violation of resolutions banning North Korea from ballistic missile-related activity.
The North responded by expelling inspectors and withdrawing from six-party talks on the disarmament of its nuclear programme.
Won Tae-jae, a South Korea defence ministry spokesman, on Tuesday defended his country's space programme saying the launch vehicle differed vastly from the North's controversial rocket launches.
He told reporters during a regular briefing that the development of South Korea's space launch vehicle has been responsible and open to the international community.
"On that matter, we are not accused of launching a ballistic missile," added Won.