Asian shares struggled on Tuesday as caution reigned ahead of this week’s U.S. Federal Reserve decision on interest rates, while the yen rose after the Bank of Japan took no new policy steps. MSCI’s broadest index of Asia-Pacific shares outside Japan erased early gains and was down 0.7 percent in afternoon trading, taking its cue from slumping Chinese shares. Japan’s Nikkei stock index (.N225) ended up 0.3 percent, though off its morning session highs.