Dredgers have been spotted off Cambodia’s Ream naval base, where China is funding construction work and deeper port facilities would be necessary for the docking of larger military ships, a U.S. think tank said Friday.

The United States, which has sought to push back against Beijing's extensive territorial claims and military expansion in the South China Sea, reiterated its "serious concerns" about China's construction and military presence at Ream.

"These developments threaten U.S. and partner interests, regional security, and Cambodia's sovereignty," a spokesperson for the State Department said.