Why do you keep trying to distort the words of Defense Secretary Mattis?
He never said the US will NOT ACCEPT Chinese militarization of the South China Sea islands "as a basis for claiming ownership," which are words that you chose to add on your own.
Look at the quote from Mattis. It plainly says the US will not accept Chinese militarization of the South China Sea islands PERIOD.
U.S. MATTIS SLAMS BEIJING OVER MILITARIZATION OF ISLANDS IN SOUTH CHINA SEA | Newsweek (June 3, 2017)
"The United States is encouraged by China's efforts to restrain North Korea but
Washington will not accept Beijing's militarization of islands in the South China Sea, U.S. Defense Secretary Jim Mattis said on Saturday."
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The New York Times said the United States showed "REMARKABLE DEFERENCE TOWARD BEIJING."
I'm trying to explain the reason the US is showing "remarkable deference" to China in the South China Sea.
Something is holding the US back from unleashing its 11 aircraft carrier battlegroups on the reclaimed Chinese militarized South China Sea islands.
That something is much more important than the South China Sea. What could that possibly be? I'm guessing 500 Chinese DF-41 ICBMs in Outer Mongolia with 5,000 thermonuclear warheads is the reason.
Trump’s Turn Toward China Curtails Navy Patrols in Disputed Zones | The New York Times (May 2, 2107)
"
The decision not to challenge China’s territorial claims represents a remarkable deference toward Beijing from an administration that is increasingly turning toward President Xi Jinping for help amid the escalating crisis in the Korean Peninsula. It remained unclear on Tuesday whether it was Defense Secretary Jim Mattis; Gen. Joseph F. Dunford Jr., the chairman of the Joint Chiefs of Staff; or one of their deputies who turned down the three requests. Defense officials said the White House was not involved." (fourth paragraph)