First IBM's PC unit, now Unocal and Maytag. Beijing has a good appetite!

A senior U.S. official also weighed in Wednesday on the potential bid by Cnooc, which trades on the New York and Hong Kong stock exchanges but is controlled by the state-owned China National Offshore Oil Corp. U.S. Energy Secretary Samuel Bodman said an attempt by Cnooc to purchase El Segundo, Calif.,-based Unocal would have to be reviewed by the Committee for Foreign Investment in the U.S., an interagency panel that examines the national security implications of foreign acquisitions of U.S. companies. Congress had already scheduled a hearing Thursday on trade tensions with China, as issues from textile imports to currency valuation have roiled lawmakers in recent months.

But the threat of U.S. protectionism is already causing a split among domestic energy producers. Tuesday, as word of a coming Cnooc bid leaked out, Exxon Mobil Corp. Chief Executive Lee Raymond said it would be a "big mistake" for the U.S. to block the bid. "You have to have free trade," Mr. Raymond said during an appearance at an energy summit sponsored by Reuters. "If you start to put inefficiencies in the system, all of us eventually pay for that."