Chinese oil company Cnooc Ltd (CEO.NYSE, 0883.HKG) has asked US regulators to review its proposed US$15.1 billion acquisition of Canadian oil and gas producer Nexen Inc (NXY.NYSE, NXY.TSE), The Wall Street Journal reported. The deal is currently undergoing a 45-day review in Canada, but due to Nexen Inc’s operations in the US Gulf of Mexico, it must also be cleared through the American regulators as compatible with US national security. “We have emphasized that the deal poses no threat to US national security,” Cnooc spokesman Peter Hunt said. Cnooc has already invested in the US including in shale assets in Texas, but this deal would be its first US deep-water operation. Cnooc insists it has complied with all laws and will continue to be subject to all regulations.