BEIJING (AP) — A major Chinese bank, the Bank of China, is cutting off business with a North Korean bank accused by the U.S. of assisting Pyongyang's missile and nuclear programs.

A spokeswoman for the Beijing-based Bank of China said Tuesday that it had notified the Foreign Trade Bank of North Korea that its accounts were being closed and all financial transactions suspended. The spokeswoman did not offer further details.

China's leadership has shown growing frustration with its North Korean neighbor and ally and a greater willingness to work with Washington in applying pressure.

The Foreign Trade Bank is North Korea's main foreign exchange bank. In imposing sanctions against it in March, the U.S. Treasury Department called it a key node in financing North Korea's weapons programs.