The US military is planning a missile defence test next week which for the first time will target an intercontinental-range missile.
The Pentagon plan is to closely simulate a North Korean intercontinental ballistic missile (ICBM) aimed at the US homeland, with the test scheduled for next Tuesday.
The US interceptor has a spotty track record, having succeeded in nine of 17 attempts since 1999 and only one in the last four.
The most recent test, in June 2014, was successful.
North Korea is now the focus of US missile defence efforts after the country vowed to create a nuclear-armed missile capable of reaching American territory.
It has yet to test an ICBM.