In the latest twist to the CNOOC/Unocal saga, the Chinese oil company late Wednesday made an unsolicited US$18.5bn bid for Unocal in an effort to scotch acquisition of the California-based firm by Chevron Corp, The Asian Wall Street Journal reported, citing sources close to the negotiations. The bid, backed by borrowing from China's treasury, underscores China's desperate need for fuel to feed its economy. State-controlled CNOOC also trades on the New York and Hong Kong stock exchanges. US Energy Secretary Samuel Bodman said CNOOC's effort to purchase Unocal must be reviewed by the Committee for Foreign Investment, an interagency group that examines foreign acquisitions of US companies and their national security implications. Exxon Mobile Corp chief executive Lee Raymond, meanwhile, said it would be a "big mistake" for Washington to block the Chinese bid. "You have to have free trade," he told a summit sponsored by Reuters. "If you start to put inefficiencies in the system, all of us eventually pay for that."