Pentagon spokesman Navy Captain Jeff Davis said a routine test of the Terminal High Altitude Area Defense (THAAD) system had been scheduled to go ahead "soon".
"These tests are done as a routine measure to make sure that the system is ready," he said.
"They are scheduled well in advance of any other real world geopolitical events going on."
A notice to mariners put out by the US Coast Guard said the test could occur as soon as Saturday.
THAAD is designed to intercept and destroy short-, medium- and intermediate-range ballistic missiles during their final phase of flight.
THAAD is not designed to stop an ICBM -- that job is left primarily to the Ground-based Midcourse Defense (GMD) interceptor system.
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