Washington, Aug 1 (IANS): An intercontinental ballistic missile (ICBM) launched on July 28 by North Korea may have disintegrated as it re-entered the Earth's atmosphere, experts have revealed.

The expert at 38 North, a US-based website that specialises in North Korea analysis, said in a report on Monday that video footage from Japanese state broadcaster NHK indicated that the missile's re-entry vehicle did not survive the second test, reports Efe news.

For an intercontinental missile to destroy a target, the re-entry vehicle must withstand extreme atmospheric conditions to maintain the trajectory of the projectile.

The NHK footage showed the re-entry vehicle beginning to glow from excessive heat about 20 km above the earth's surface as it descends, according to the researchers.

The vehicle then slows down and appears to shed small radiant objects and was trailed by an incandescent vapour. At an altitude of 3 to 4 km, it then dims and quickly disappears before falling into the Sea of Japan.

This indicated that the re-entry vehicle "disintegrated about the time it experienced maximum stressing loads" during re-entry, the researchers said.

"If this assessment accurately reflects reality, North Korea's engineers have yet to master re-entry technologies and more work remains before Kim Jong-un has an ICBM capable of striking the American mainland," the report said.

The Hwasong-14 missile launched covered about 1,000 km and reached a maximum height of more than 3,700 km, leading experts to predict it could reach major US cities.