WASHINGTON - US Defense Secretary Ashton Carter will depart today for an Asian security summit in Singapore, where Beijing’s military expansion across the South China Sea likely will once again dominate discussions.

Regional neighbors are fretting over what they see as China’s expansionism as it rushes to exert sovereignty over the waterway, a major global shipping route believed to be home to large oil and gas reserves.

China is using dredgers and other tools to convert low-lying ocean features and sandy blips into military bases.

A Pentagon report this month said China has added more than 3,200 acres (1,300 hectares) of land to the seven features it occupies in the Spratly Islands archipelago.

The so-called Shangri-La Dialogue, an annual meeting in Singapore, will see defense ministers, military chiefs and defense experts from the Asia-Pacific region and beyond discuss regional security issues.

Aside from the South China Sea, delegates are expected to focus on the growing threat of Islamic terrorism in the region and North Korea’s nuclear programme.

Since becoming President Barack Obama’s fourth Pentagon chief in February 2015, Carter has taken a forceful tone on Beijing’s South China Sea construction.

He criticised the drive at last year’s Shangri-La meeting and on Friday, Carter said China risks creating a "Great Wall of self-isolation."

"Countries across the region -- allies, partners and the unaligned -- are voicing concerns publicly and privately at the highest levels," Carter said.

The United States has conducted several "freedom of navigation" operations where it pointedly ignores China’s claims of sovereign exclusion zones around the islands by closely flying or sailing past.

Carter’s trip will see him first visit an Army base in Arizona.

He had also considered meeting his Japanese counterpart Gen Nakatani during a visit to Japan, but the two decided to meet in Singapore instead, a US defense official said on condition of anonymity. — AFP