* BOJ ready to adjust policy downward, upward - Kuroda

* Implication of negative rates on economies unclear

* Expectation of prolonged BOJ easing weighs on yen

By Leika Kihara

TOKYO, Nov 25 (Reuters) - Bank of Japan Governor Haruhiko Kuroda on Monday stressed the bank's resolve to maintain its ultra-loose monetary policy and expand stimulus further if risks to the economy threaten its 2 percent price target.

Kuroda, however, shrugged off negative interest rates as a realistic option for central banks even as they become increasingly reliant on unconventional steps to stimulate their economies, pointing out that the implications for an economy remained unclear.

"Negative short-term interest rates could be possible and (may have been) experimented with in some countries in the past. But that's only to some extent and for quite a short time," he said in a seminar.

Expectations that the BOJ will stick to its aggressive stimulus policy - under which it pledged to double base money via asset purchases to accelerate inflation to 2 percent in roughly two years - have weighed on the yen, pushing it to a six-month low against the dollar on Monday.

Kuroda said that while the BOJ's price target is "ambitious," he expects Japan to reach it sometime late next fiscal year or early fiscal 2015, which ends in March 2016.

He stressed that the BOJ will continue its ultra-easy policy "in coming months and years" to achieve its 2 percent inflation target in a stable matter.

"Of course there are downside and upside risks," Kuroda said, adding that the BOJ is willing "to adjust its policy as necessary, if necessary, either downward or upward depending on the nature of the risks."

As widely expected, the BOJ kept monetary policy steady last week and maintained its upbeat assessment that the world's third-largest economy was recovering moderately. It has stood pat on policy since adopting in April its aggressive stimulus that pledged to achieve 2 percent inflation in two years.