Chinese development on a South China Sea islets claimed by the Philippines would prompt "actions being taken" by the United States and other nations, US defense chief Ashton Carter said Saturday.

"I hope that this development doesn't occur because it will result in actions being taken both by the United States, and actions being taken by others in the region that will have the effect of not only increasing tensions but isolating China," Carter told a Singapore security summit. 

Hong Kong media this week reported China plans to establish an outpost on Scarborough Shoal, 230 kilometres (143 miles) off the Philippine coast, which Manila says lies in its exclusive economic zone.