President Barack Obama said on Thursday the United States is concerned China uses its “sheer size and muscle” to push around smaller countries in the South China Sea. His comments come after China defended its construction of artificial islands in the South China Sea, saying it is needed to safeguard its sovereignty in the mineral-rich waters where China’s territorial claims overlap those of Vietnam, the Philippines, Malaysia, Brunei and Taiwan. “Where we get concerned with China is where it is not necessarily abiding by international norms and rules and is using its sheer size and muscle to force countries into subordinate positions,” Obama told town-hall event in Jamaica ahead of a Caribbean summit in Panama, where he hopes to reassert U.S. leadership in Latin America.