Bank of America cut business with North Korea 's main foreign exchange exchange . Move from U.S.-led sanctions to increase funding for Pyongyang 's nuclear program . China is North Korea 's closest economic ally . China is by far North Korea 's most important formal ally , and overwhelmingly its biggest trading partner . Move ##s also reflect bank risk management rather than bigger diplomatic motive .
Bank of America cut business with North Korea 's main foreign exchange exchange . Move from U.S.-led sanctions to increase funding for Pyongyang 's nuclear program . China is North Korea 's closest economic ally . Move ##s also reflect bank risk management rather than bigger diplomatic motive .