The US 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, Defense Secretary Ash Carter said on Tuesday.
North Korea declared on Sunday it could test-launch an ICBM at any time from any location set by leader Kim Jong Un, saying a hostile US policy was to blame for its arms development.
"If the missile is threatening, it will be intercepted. If it's not threatening, we won't necessarily do so," Carter said in his final news briefing before President Barack Obama's administration leaves office on Jan. 20.
"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."
The top US military officer, Marine General Joseph Dunford, who will stay in his role as chairman of the Joint Chiefs of Staff, concurred with Carter at the event but did not enter into specifics. Carter's language left open the possibility of US military action in any scenario.
Carter's remarks came just over a week after US President-elect Donald Trump vowed that North Korea would never fulfil its threat to test an ICBM. Trump said in a Jan. 2 tweet: "It won't happen!"
Preventing an ICBM test is far easier said than done, and Trump has given no indication of how he might roll back North Korea's weapons programs after he takes office, something successive US administrations, both Democratic and Republican, have failed to do.
A 2016 assessment released by the Pentagon's weapons testing office on Tuesday said that US ground-based interceptors meant to knock out any incoming ICBM still had low reliability, giving the system itself a limited capability of shielding the United States.
Once fully developed, a North Korean ICBM could threaten the continental United States, which is around 9,000 km (5,500 miles) from the North. ICBMs have a minimum range of about 5,500 km (3,400 miles), but some are designed to travel 10,000 km (6,200 miles) or farther.