The Bank of Japan expanded its fund supply tool at an emergency meeting on Monday, saving more aggressive steps for when there is clearer evidence of a slowdown in a fragile economy hit by a strong yen.
The central bank increased the volume of money available to banks under its fixed-rate fund supply operation to 30 trillion yen ($351 billion) from 20 trillion yen.
It also put in place a six-month fund operation in addition to the three-month loan programme already in place.
Of the 30 trillion yen, 10 trillion yen will be the six-month fund operation, BOJ said.
The decision was by an 8-1 vote, with Miyako Suda dissenting.
The central bank, as widely expected, maintained its overnight core rate target at 0.1 percent by a unanimous vote.
Shirakawa will hold a news conference to explain the decision at 2:30 p.m. (0530 GMT)
(Reporting by Leika Kihara, Tetsushi Kajimoto; Editing by Edmund Klamann)