US president Barack Obama expressed concern over China was using its "sheer size and muscle" to push around smaller nations in the South China Sea, inviting a swift rebuke from Beijing, accusing the US of being the bully.
China reclaimed seven reefs in the Spratly archipelago of the South China Sea alarming other claimants, such as the Philippines and Vietnam.
The move prompted criticism from US government officials and the military.
While the new islands would hardly hurt US military superiority in the region, with China building ports and fuel storage depots and possibly two airstrips that according to experts would allow Beijing to project power deep into the maritime heart of Southeast Asia, the concern may not be misplaced according to commentators.
"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 a town-hall event in Jamaica on Thursday ahead of a Caribbean summit in Panama.
"We think this can be solved diplomatically, but just because the Philippines or Vietnam are not as large as China doesn't mean that they can just be elbowed aside," he said.
Earleir, China defended its construction of artificial islands, saying it was needed to safeguard its sovereignty in the mineral-rich waters where China's territorial claims ran close to those of Vietnam, the Philippines, Malaysia, Brunei and Taiwan.
According to Chinese officials, the reclamation work would support military defence provide services that would benefit other countries.
According to the State Department, the activity was causing anxiety in the region about China's intentions.
Speaking to young people in Jamaica, Obama further said the US encouraged Chinese investments around the world, but the deals needed to benefit the people of those countries.