China risks further alienating regional neighbours and building a “great wall of self-isolation” as it pursues its military expansion across the South China Sea, US defense secretary Ashton Carter warned on Saturday.

Speaking at a security summit in Singapore, Carter said countries across the Asia-Pacific region continue to fret over China’s sweeping claims of sovereignty in the South China Sea, and its attempts to bolster these by creating military bases on reclaimed islets and increasing maritime patrols.

“China’s actions in the South China Sea are isolating it, at a time when the entire region is coming together and networking,” Carter said in a speech at an annual forum known as the Shangri-La Dialogue.

“Unfortunately, if these actions continue, China could end up erecting a great wall of self-isolation.”