The Bank of Japan added to its toolkit by abandoning a minimum return on bonds it purchases, a step that may ensure it meets targets for adding stimulus to the economy even as a goal of ending deflation remains out of reach.

The BOJ scrapped the requirement for regular purchases of government debt, currently set at 1.8 trillion yen ($23 billion) a month, and for notes that it accumulates under a 55 trillion yen asset-purchase fund. Policy makers also yesterday expanded the asset program by 10 trillion yen.

The central bank's move may avert repeats of failures this year at operations where the BOJ was unable to persuade bondholders to sell enough securities to meet its targets. Investors flocked to bonds as a haven as the world's third- largest economy slowed to what the BOJ termed a pause in growth, sending yields on three-year securities to 0.1 percent.

"The Bank of Japan really wanted to smooth the way for carrying out bond purchases, to make sure that asset purchases can be completed," said Shogo Fujita, chief Japanese bond strategist at Bank of America Merrill Lynch in Tokyo. "It also opened the door for negative rates."