Washington (CNN) The U.S. "sees indications" that North Korea is "likely preparing" for some type of weapons test in association with the 70th anniversary of the founding of the ruling Workers Party on October 10, a U.S. official told CNN.

A likely scenario is that North Korea will attempt, for the first time, to test a submarine-launched medium-range ballistic missile at sea off its eastern coast, according to two U.S. officials familiar with the latest intelligence. The test is seen by the U.S. as part of the regime's "usual provocative efforts."

In May, the regime published photos of what it said was leader Kim Jong Un standing in front of a submarine at sea, launching a missile, but U.S. intelligence experts said there was no electronic, infrared or satellite data to suggest a launch had occurred and that only the on-board ejection system was tested.

So far, there is no international notice for ships to remain out of any particular area in anticipation of a test, the official added. North Korea could also fire some short-range missiles, a more typical maneuver by the regime. Several U.S. officials said some type of "show of force" by the regime has been planned, but the exact timing remains to be seen.

U.S. and international monitors are also closely watching land-based missile launch sites and known nuclear test facilities for any indications of activity.

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