China has again warned the United States of the severe consequences caused by its arms sales to Taiwan, saying the move will undermine Sino-US cooperation.The Foreign Ministry spokesman, Jiang Yu said in a statement on Thursday that China firmly opposes the arms sales to Taiwan by the United States.Jiang's remarks came amid reports that the U.S. Defense Department had recently awarded Lockheed Martin Corp contract for an unspecified number of advanced Patriot missiles to be sold to Taiwan.