The United States called on China on Saturday to stop "bullying behavior" in the South China Sea and said it was concerned by reports of Beijing's "provocative actions" aimed at offshore oil and gas developments in the disputed waters.Three regional security sources told Reuters on Friday that a Chinese government survey ship was tagging an exploration vessel operated by Malaysia's state oil company Petronas in those waters.The vessel Haiyang Dizhi 8 was earlier this week spotted off Vietnam, where it had last year conducted suspected oil exploration surveys in large expanses of Vietnam's exclusive economic zone."The United States is concerned by reports of China's repeated provocative actions aimed at the offshore oil and gas development of other claimant states," the U.S.