He added that "if low confidence in the missile's reliability is acceptable, two or three test firings over the next four to six months may be all that is required before Kim Jong Un declares the Hwasong-15 combat ready".
The blockade became a center of inquiry after Defense Minister Song Young-moo said Seoul would be compelled to take part in sanctions along with the United States, should Washington call for a blockade, The Korea Times reported.
Moon said it was not clear whether the communist nation has in fact built nuclear weapons, let alone perfected its missile technology.
Pyongyang heralded the launch as the completion of its nuclear force capable of striking anywhere in the U.S.
South Korea said it expected Pyongyang to pause its provocative missile testing program following Wednesday's successful flight of its new Hwasong-15 missile, which can reach the USA mainland.
"The government does not think that North Korea's latest test demonstrated full capability for an ICBM, including the re-entry technology and a precision guidance system".
Earlier on Thursday, Pentagon Chief James Mattis said that the USA intends to "tirelessly" seek to resolve the North Korean nuclear issue with the help of the United Nations and will make diplomatic efforts to persuade Pyongyang to abandon the programs for the development of nuclear weapons and their means of delivery.
The Hwasong-15 is longer than the Hwasong-14 by 2 metres (6.56 feet) and also thicker, particularly its second stage, which is 80 centimetres (2.62 feet) wider than Hwasong-14's second stage, Seoul's Defence Ministry said.
"We must prevent a situation in which North Korea misjudges the situation and blackmails us with nuclear weapons or in which the United States contemplates a preemptive strike", Moon said during a full session of the National Security Council (NSC) over which he presided on the day of North Korea's missile test launch. In order to curb further provocations from the North, U.S. strategic assets will continue to be rotated on and near the Korean peninsula until the Pyeongchang Winter Olympics next February, Yeo said.
"For now if there are no sudden changes in situation or external factors, we feel there is a high chance North Korea will refrain from engaging in provocations for a while", said Lee Yoo-jin, deputy spokeswoman at the Unification Ministry. It's also considerably larger than North Korea's previous ICBM, the Hwasong-14, and created to deliver larger warheads, the ministry said.
North Korea is known to test fewer missiles in the fourth quarter of the year as troops are called to help with harvests, while the cold temperature is a strain on its fuel supplies. To do so, the two leaders will continue to apply strong sanctions and pressure to bring the rogue regime to talks. That was the response Moon made when Trump asked him what he thought about North Korea's missile.