Defense Minister Shin Won-sik has assessed that North Korea's recent test of a hypersonic missile was not successful and the missile development is still "incomplete."

Appearing on a KBS program on Sunday, the minister presented the assessment refuting Pyongyang's claim on April 3 that it successfully tested a new intermediate-range solid-fuel hypersonic ballistic missile.

Shin said that hypersonic missiles should be able to do the so-called glide flight at the terminal phase, flying at the speed of Mach five, but a detailed analysis by South Korea and the United States assessed that the North Korean missile did not succeed in the glide flight in the final stage.

However, the minister acknowledged some technological progress, citing the change in the missile's warhead from a conical shape to a glide-type, projecting that the North will ultimately succeed in the development of a hypersonic glide missile because it is making all-out efforts into the development.

Regarding North Korea's possible launch of its second military spy satellite, the minister said that Pyongyang may conduct the launch as early as this weekend or a few days later, adding that the launch will come late April at the latest.

Shin said that South Korea has been closely monitoring signs that the North had been preparing for a launch on April 15, the birth anniversary of the North's late founder Kim Il-sung, but North Korea appears to be making some tests and technical complementary measures.