North Korea says the missile it launched Sunday is capable of carrying a nuclear warhead.
The North's Korean Central News Agency said the launch was "aimed at verifying the tactical and technological specifications" of the new long-range ballistic missile.
And the state-owned media outlet claims the rocket can hold a "large-size, heavy nuclear warhead."
Officials in South Korea say they need more information before they can confirm the North's nuclear warhead claims.
But experts believe this latest launch was North Korea's most successful missile test ever.
And some say it's a sign the country is getting closer to developing an intercontinental ballistic missile capable of reaching the U.S. mainland.
Still, U.S. officials said the type of missile fired during Sunday's test was "not consistent" with an ICBM. And some analysts believe it could take North Korea years to master the technology needed to build a reliable one.