Bank of Japan Policy Board member Ryuzo Miyao said the bank needed to boost asset-purchase programs by ¥10 trillion amid an increase in downside risks for the economy, the minutes from last month's board meeting show.
Miyao, 47, proposed that the BOJ expand its asset-purchase fund to buy more government bonds, according to the record of the Oct. 27 gathering. The Policy Board decided to increase the program by half that amount, bringing its total size to ¥20 trillion.
Europe's sovereign debt crisis is the "largest risk" to Japan's export-driven growth, and some Policy Board members have become more cautious about the economy's outlook since last month, BOJ Gov. Masaaki Shirakawa said last week.
Board members may be already weighing the need for additional stimulus, said analyst Naomi Hasegawa.
"Their cautiousness about the Japanese economy has intensified a lot since the October meeting, when they eased policy," said Hasegawa, a senior bond strategist at Mitsubishi UFJ Morgan Stanley.
The BOJ last week cut its monthly economic assessment for the first time since April, citing a global slowdown, the yen's appreciation and the effect of Thailand's flooding on supply chains and exports.
It held the overnight lending rate between zero and 0.1 percent and maintained the size of credit and asset purchase programs.
The fund buys assets, including government bonds, corporate debt and exchange-traded funds. A few Policy Board members said that purchases of bonds with maturities of up to two years are effective in stabilizing the foreign-exchange market.