The South Korean military suspects that a problem with the combustion system in the engine of North Korea's launch vehicle was the main cause of its failed military spy satellite launch late Monday.

A Joint Chiefs of Staff(JCS) official said on Tuesday that additional analysis is required due to the vehicle exploding in midair in the early stages after liftoff, saying it is suspected that there could have been a problem with the combustion system, citing the explosion of the first-stage propellant.

Through the state-run Korean Central News Agency(KCNA), Pyongyang admitted that the satellite launch had ended in failure, explaining that there had been a midair explosion of the new rocket's first-stage propellant.

It cited the insufficient reliability of the new liquid oxygen-petroleum engine as the cause.

The JCS official forecast said it would take a considerable amount of time for the North to prepare for another satellite launch, saying the country did not announce additional launch plans in contrast to the two previous failures last year.