North Korea's test of its first submarine-launched ballistic missile is set for Sept. 9, the 72nd Foundation Day of the communist state. U.S. weapons experts agree North Korea is preparing to test what's likely its first SLBM that might one day give North Korean nuclear submarines a first strike capability against the United States.

The Center for Strategic and International Studies (CSIS) on Saturday posted new and vivid satellite images taken Friday indicating North Korea is preparing its first SLBM test. The SLBM will likely be launched from the only SINPO-C ballistic missile submarine (SSB) in service with the Korean People's Navy (KPN).

Dr. Victor Cha of CSIS said the images show a submersible test stand barge at the Sinpo South Shipyard in South Hamgyong province along the Sea of Japan. He said the strongest indicator suggesting preparations for an SLBM test launch is the presence of several ships within the basin.

One of these ships might have been used to tow the test barge out to sea. Another indicator is two Romeo-class diesel-electric submarines anchored within the Mayang-Do Naval Base. Experts say these subs, of which there are 20 in North Korea, might be used as escorts for the SINPO-C SSB.

Sinpo South Shipyard produced North Korea's only SINPO-class submarine, the largest submarine designed and built for the KPN. The SINPO-C SSB and the SINPO-class experimental ballistic missile submarine (SSBA) were both built at Sinpo South Shipyard.

Cha said this looks like they're certainly preparing to do an SLBM test for the first time.

He said North Korean supreme leader Kim Jong-un has been talking a lot about unveiling a new strategic weapon "and this may be it. There's been a lot of activity around this one site where the test barge is located."

U.S. President Donald Trump and Kim met in Singapore on June 12, 2018, and in Hanoi, Vietnam last Feb. 27 to 28. The summits achieved little  in the way of convincing Kim to abandon his nuclear weapons development program.

Trump has since turned a blind eye toward Kim's resumption of missile and rocket tests, claiming these were short-range weapons. This excuse won't hold with the launch of the intercontinental SLBM, which will clearly violate the conditions imposed by U.S. and UN sanctions on North Korea.

"A sea-launched missile test would definitely cross all of President Trump's red lines because it would involve a major ballistic missile," according to Cha. "It would be difficult for President Trump to ignore this."