ReutersThe Bank of Japan building in TokyoThe Bank of Japan left its main policy unchanged Tuesday despite a tumbling inflation rate, indicating it is still confident that prices will resume their upward trend later in the year without the need for additional action. The central bank expects cheaper energy prices and expected wage increases at major companies to eventually stimulate consumer spending, boosting growth and helping the bank achieve its 2% inflation target by around spring 2016. In a statement issued after a two-day meeting, the BOJ said its policy board voted 8-1 to keep unchanged the size of the bank’s annual asset purchases at ¥80 trillion ($660 billion). Faced with the plunging energy prices, the central bank last October took the lead among a number of global central banks in easing credit to stamp out deflation concerns and shore up its flagging economy. Toko Sekiguchi contributed to this article. An expanded version of this report appears on WSJ.com.