(CNN) Aerial photos taken by the US Navy show just how close a US Navy ship came to colliding with a Chinese warship that had challenged the US vessel's presence in the South China Sea.

The guided-missile destroyer USS Decatur was performing a "freedom of navigation" operation on Sunday, sailing close to Chinese-claimed reefs in the Spratly Islands, when it was approached by a Chinese destroyer, the Lanzhou.

The two ships could have been seconds away from a collision, said Carl Schuster, a former US Navy captain with 12 years at sea who looked at the photos at the request of CNN.

At this point, the US ship has "slammed on the brakes" and moved to its right to avoid colliding with the Chinese vessel, said Schuster.

Taken by a US Navy aircraft but not released by the US Navy, the four photos were verified for CNN by three US officials. They were published on the gcaptain blog site , which describes itself as an "interactive community of maritime professionals."

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