U.S. President Barack Obama sought to reassure allies in Asia last month that the United States would support them in the face of a more assertive China.
But after one of Beijing's boldest moves in years to lay claim to contested waters off Vietnam, some Asian countries are asking a simple question: Where is Washington?
Days after Obama left the region, China deployed an oil drilling rig 150 miles (240 km) off the coast of Vietnam, into a part of the South China Sea claimed by itself and Hanoi. That sparked deadly anti-China riots in central Vietnam and raised questions over whether Obama's long-promised strategic "pivot" of military assets to Asia is more than talk.