The North's missile capability "is getting sophisticated at a fast pace in all aspects, including flight distance and time," he said.

During its 53-minute flight, the North's missile traveled 950 kilometers at an apogee of 4,475 km to splash into the East Sea. The missile was apparently fired at a lofted angle. If done at a standard one, it could have gone far over 10,000 km, given its maximum altitude, experts said.

Lee said the North appears to have carefully designed the launch in a way that demonstrates its capabilities without provoking the international community too much as the regime didn't fly it toward Hawaii or the US territory of Guam.

The launch marked the North's first provocation in more than two months since Sept. 15.

Lee said the US decision to relist Pyongyang as a state sponsor of terrorism could have been a factor that prodded the North to go ahead with the launch.

Lee said South Korea will work closely together with the international community to pursue stronger sanctions and pressure against the North, saying it's "unrealistic" to choose dialogue at a time when the North is stepping up its missile provocations.

"Perhaps, I think we need to consider our unilateral sanctions," he said without elaborating.

Lee also said that military force is one of the US options to deal with the North, but Washington is expected to consult closely with Seoul before taking any action. (Yonhap)