The U.S. Commerce Department on March 8 officially put into place export restrictions on the sale of equipment by U.S. companies to Chinese telecom manufacturer ZTE Corp., the world's seventh-largest producer of smartphones. The restrictions, which will severely hamper ZTE's supply chain, come in response to the Chinese conglomerate's sale of U.S. technology to Iran in violation of sanctions. The incident represents the latest flare-up between the United States and China over technology manufacturing. The restrictions on ZTE will hinder its ability to use chips made by Qualcomm, Intel or any other U.S. manufacturer in its smartphones and will limit its access to optical equipment for cameras. Since Beijing's rivals — South Korea, Taiwan, Japan and, of course, the United States — dominate these sectors, the sale of these parts is perhaps the most powerful trade lever that those countries can use against China.