WASHINGTON (Reuters) – A high-tech sea-based U.S. military radar has left Hawaii to monitor for potential North Korean intercontinental ballistic missile test launches, a U.S. defense official said on Wednesday.

Earlier this month, North Korean leader Kim Jong Un said that the isolated, nuclear-capable country was close to test-launching an intercontinental ballistic missile (ICBM).

The official, speaking on condition of anonymity, said the radar, known as the Sea-based X-band radar (SBX), left on Monday and would reach its destination, about 2,000 miles (3,218 km) northwest of Hawaii, towards the end of January.

The radar is able to track ICBMs and differentiate between hostile missiles and those that are not a threat.

On Tuesday, U.S. Defense Secretary Ash Carter said the U.S. military might monitor a North Korean intercontinental ballistic missile test and gather intelligence rather than destroy it, as long as the launch did not pose a threat.

“If the missile is threatening, it will be intercepted. If it’s not threatening, we won’t necessarily do so,” Carter said,

“Because it may be more to our advantage to, first of all, save our interceptor inventory, and, second, to gather intelligence from the flight, rather than do that (intercept the ICBM) when it’s not threatening.”

Carter’s remarks came just over a week after U.S. President-elect Donald Trump vowed that North Korea would never fulfill its threat to test an ICBM. Trump said in a Jan. 2 tweet: “It won’t happen!”

“The SBX’s current deployment is not based on any credible threat; however, we cannot discuss specifics for this particular mission while it is underway,” Commander Gary Ross, a Pentagon spokesman, said.

(Reporting by Idrees Ali and Phil Stewart; Editing by James Dalgleish)