The United States said on Thursday it is deeply concerned about China's interference in oil and gas activities in waters claimed by Vietnam, saying this called into serious question Beijing's commitment to peaceful resolution of maritime disputes.

A State Department statement said China’s redeployment of a government-owned survey vessel, together with armed escorts, into waters off Vietnam on Aug. 13 was "an escalation by Beijing in its efforts to intimidate other claimants out of developing resources in the South China Sea."