North Korea's latest intercontinental ballistic missile did not survive re-entry into the Earth's atmosphere after it was tested this week, a U.S. official told Fox News Saturday.

The official added that U.S. allies are searching for the remnants of the warhead after it splashed down close to the Japanese coast Wednesday.

The news suggests that even if North Korea's latest missile, dubbed the Kwasong-15, could not make impact on U.S. soil even if it has the range to reach American shores. South Korea's Defense Ministry said Friday that the two-stage liquid-fuel missile potentially capable of striking targets as far away as 8,100 miles, which would put Washington within reach.

South Korean President Moon Jae-in shared his country's assessment with President Donald Trump in a telephone conversation Thursday night. The leaders reaffirmed their commitment to strengthen pressure and sanctions on Pyongyang to discourage its nuclear ambitions, Seoul's presidential office said Friday. Eugene Lee, spokeswoman of South Korea's Unification Ministry, which deals with affairs related to North Korea, said the Seoul government thinks the North hasn't crossed the "red line" in weapons development yet because it hasn't perfected its ICBMs.

North Korea said the missile on Wednesday reached an apogee of 2,780 miles and flew 600 miles, flight data similar to what was announced by South Korea's military. Pyongyang described its new ICBM as "significantly more" powerful than the Hwasong-14, which the North flight tested twice in July.

The Hwasong-15 is longer than the Hwasong-14 by 6.56 feet and also thicker, particularly its second stage, which is 2.62 feet wider than Hwasong-14's second stage, Seoul's Defense Ministry said.

Hwasong-15's 9-axle transport vehicle, which the North also revealed for the first time, was also 6.56 feet longer than the 8-axle truck the North used to carry the Hwasong-14s.

The Hwasong-15's first stage is powered by a pair of engines that were also used in the single-engine first stages of the Hwasong-14, the ministry said. It was still working to analyze the construction of the second stage.

Fox News' Jennifer Griffin and The Associated Press contributed to this report.