U.K. stocks gained ground Tuesday, finding support as the pound lost some of its value ahead of much anticipated decisions by the U.S. Federal Reserve and the Bank of Japan. The blue-chips benchmark had been darting in and out of positive territory Tuesday, but stepped higher as the pound GBPUSD, -0.1694% dropped below $1.30, trading below that level for the first time since mid-August.

U.S. stocks on Tuesday ended little-changed, paring modest gains into the close, as traders grew cautious on the eve of a pair of major central-bank decisions. Volatile oil prices pressured energy shares, limiting overall gains. The S&P 500 index SPX, +0.03% finished up less than a point at 2,139.76. Health care and consumer staples led winners, while energy shares lagged behind, falling 0.8%.

Japan's Nikkei stock market rose and the yen weakened immediately following the BOJ announcement. Japan's central bank announced Wednesday that it would keep its key interest rate steady at -0.1%. The Bank of Japan also said it would expand its monetary base until inflation becomes stable above 2%. The BOJ intends to abandon its monetary base target, but maintain an annual pace of government-bond buying at 80 trillion yen. Experts had been nervously awaiting the bank's move, with many concerned the BOJ would cut interest rates even deeper into negative territory.