Story highlights North Korea still faces hurdles, the director of the Defense Intelligence Agency said

The testimony came days after a North Korean ballistic missile test

(CNN) North Korea will eventually obtain a nuclear weapon capable of hitting the United States if left unchecked, a top US intelligence official said.

"If left on its current trajectory, the regime will ultimately succeed in fielding a nuclear-armed missile capable of threatening the United States homeland," said Lt. Gen. Vincent Stewart, the director of the Defense Intelligence Agency. "While nearly impossible to predict when this capability will be operational, the North Korean regime is committed and is on a pathway where this capability is inevitable."

The only hurdle left, Stewart said in a hearing before the Senate Armed Services Committee on Tuesday, is finding a way for its ballistic missile to re-enter the atmosphere. Perfecting re-entry is "really a matter of enough trial and error to make that work," Stewart said. "They understand the physics, so it's just a matter of design."

Ballistic missiles fly in a parabolic route, exiting and entering the Earth's atmosphere, while cruise missiles fly in a straight line within the atmosphere.

Stewart and Director of National Intelligence Dan Coats spoke days after North Korea tested its second ballistic missile in the span of a week.

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