Bank of Japan policymakers are expected to stick to their massive easing measures after they wrap up a two-day meeting on Thursday.
BOJ Governor Kuroda Haruhiko will announce the policy direction shortly after the meeting.
Market participants want to know what the central bank will do if the yen continues its slide against the US dollar.
A further widening in the interest-rate gap between Japan and the US could accelerate yen selling, as investors seek higher yields in the US.
The government and the central bank have raised their alert levels on the yen's accelerating depreciation.
Finance Minister Suzuki Shunichi commented on Wednesday last week, when the Japanese currency neared 145 to the dollar. He said the government would do whatever was necessary, including market intervention. He added that any such action would come instantly.
On the same day, the BOJ conducted a rate check on commercial banks, a possible sign the government and the central bank are preparing for currency intervention.
The move has fueled caution in some financial markets that the yen's rapid weakening would prompt the government and the BOJ to move ahead and sell the dollar while buying the yen.