The Chinese government continues to claim Taiwan as its territory and says it must come under its control.
Tokyo and Washington agreed in 2012 to relocate about 9,000 of the 19,000 Marines stationed on Okinawa, including 4,000 to Guam in phases.
The littoral combat ship Savannah will dock at the port of Sihanoukville on the Gulf of Thailand on Dec. 16-20.
U.S. lawmakers warn a weak military industrial base could invite aggression with China.
