China asked foreign banks to form business units to monitor their risks in yuan trading, the latest nudge at overseas banks to establish deeper operations in the country, the Wall Street Journal reported.   The effort reflects a desire by regulators to see foreign banks structure full banking operations in China rather than simply extend branch networks that are legally owned from overseas.   "Over time as the market grows, it would not be surprising for the foreign banks to be beefing up the risk-management functions relating to their onshore operations," said Thomas Jones, a law partner at Allen & Overy, to the paper. In reality, China's foreign-exchange market remains highly regulated and dominated by local companies.   The paper pointed out the irony that language also makes the Chinese market unique: Yesterday's statement, for instance, was published only in Chinese, calling on foreign bankers to "fully understand China's financial market."