About 10 percent of the Canadian oil producer's assets are in the US. A CNOOC spokesman on Wednesday reiterated that the deal does not threaten US security. CNOOC declined to comment on the precise date when the company filed its paperwork with the Committee on Foreign Investment in the US. [Businesses Registration]

The confidential panel, which is chaired by Treasury Secretary Timothy Geithner and includes the secretaries of state and defense, has up to 75 days to decide whether to impose any conditions on the deal from the day the paperwork was filed.