The Bank of Korea (BOK) decided Tuesday to keep this month's overnight call rate at 4.25 percent on concerns about internal and external economic conditions. The bank said the decision, made at a meeting of its monetary policy committee, is due to the nation's teetering stock market led by unstable U.S. financial mark market, and the strong won which is easing inflationary pressures. The call rate, charged on inter-bank loans, is the country's benchmark short-term interest rate.