The Bank of Japan kicked off a two-day policy meeting Tuesday amid growing speculation that the BOJ may further loosen its monetary grip after carrying out a "comprehensive assessment" of the aggressive easing steps it has implemented over the past three years.

BOJ Gov. Haruhiko Kuroda said in a Sept. 5 speech in Tokyo that the assessment is intended to analyze what has prevented the central bank from achieving its 2 percent inflation target, and what should be done to reach that goal.

Depending on the assessment's result, the BOJ, led by Kuroda since March 2013, may decide to expand its negative interest rate policy in a bid to spur domestic demand via rock-bottom lending interest rates, sources familiar with BOJ officials' thinking said.

But the bank is unlikely to drastically deepen the negative interest rate as corporate executives have criticized the policy. They say it has driven down longer-term interest rates, sapping the banking sector's profits and hurting returns for insurers and pension funds.

To dispel such criticism, the BOJ may tweak the framework of its bond-buying program to curb falls in longer-term interest rates by increasing its holdings of shorter-term bonds. In the meantime, the bank would retain its target of ¥80 trillion in annual government bond purchases. Interest rates move inversely to bond prices.