The Bank of Japan faces a tough decision at its Policy Board meeting later this week. Should it declare a formal end to its near-zero interest rate policy, adopting a more conventional monetary stance, or should it hold off until it is clear the economic stagnation that has haunted the country over the last 15 years is gone for good?

Whatever step the central bank takes -- or doesn't -- at the meeting, it is sure to face criticism, leaving it open to political pressure in the future, experts believe.

This is especially true given the ruckus caused by BOJ Gov. Toshihiko Fukui's investment in a fund led by Yoshiaki Murakami, who has been charged with insider trading.