It was South Korea's third attempt to put a satellite into orbit and comes after North Korea succeeded in launching a rocket in April that it said was carrying a satellite, only to abort the mission early in its flight.

Friday's failure also puts South Korea far behind economic rivals China, India and Japan.

South Korean officials at the Korea Aerospace Research Institute (KARI) that is conducting the launch said Russian engineers had found a leak in the sealing while injecting helium gas into the first-stage booster.

The rocket will be taken off its launch pad and moved to a hangar to repair the faulty seal, which will require at least three days, the officials said.

"If the problem is serious, we may not be able to launch in the current window," KARI President Kim Seung-jo said. South Korea has set a launch window of October 26 to 31. The officials indicated a new window may have to be set.

South Korea's second launch attempt in 2010 ended 137 seconds into flight when the rocket exploded before sending its payload into orbit. The first attempt in 2009 also failed when the rocket failed to release the payload.

South Korea's launch attempts have riled North Korea, which had been hit with U.N. sanctions for its rocket tests, which the reclusive state says are aimed at putting a satellite into orbit, but which critics say are tests for a ballistic missile program aimed at delivering a nuclear payload.

North and South Korea remain technically at war after an armistice rather than a peace treaty ended the 1950-53 Korean War.

(Reporting by Jack Kim; Editing by Robert Birsel)

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