The U.S. Department of Defense said the United States is closely watching North Korea's missile program.

Pentagon spokesperson Brig. Gen. Pat Ryder made the remarks on Tuesday during a press briefing when asked about the possibility of North Korea using an underground silo in its latest short-range ballistic missile launch.

Ryder said that the U.S. has long been aware of the challenges associated with North Korea's missile program, adding that it is something that the U.S. continues to watch and monitor very closely.

The spokesperson said that it is also something the U.S. maintains consultations on with its allies and partners in the region.

North Korea launched a tactical ballistic missile on Sunday and experts observed that the North might have used an underground silo for the missile test, citing the V-shaped flames at the time of the launch.