US warship

The USS Dewey sailed within 12 miles (20 kilometers) of Mischief Reef, in the Spratly Island chain, on Wednesday, in a "freedom of navigation operation," according to a US official.

While he didn't confirm details of this particular operation, Pentagon Spokesperson Capt. Jeff Davis told CNN, "We operate in the Asia-Pacific region on a daily basis, including in the South China Sea."

"We operate in accordance with international law. We fly, sail, and operate wherever international law allows," he added.

In its latest mishap, the USS Montgomery, an Independence-class LCS that's been in service less than two months, sustained an 18-inch-long crack to its hull while passing through the Panama Canal en route to its homeport in San Diego.

The Montgomery (LCS-8) was traveling from the Atlantic to the Pacific Ocean through the canal's series of "locks" when it hit a cement structure known as the "center lock wall" while under the control of a local Panama Canal pilot, according to a statement to CNN from the Navy.