Tokyo stocks rose 1.23 percent at the open Wednesday, tracking a rise on Wall Street and as the dollar climbed on speculation that the Fed would further reduce its stimulus.
The Nikkei-225 index was up 184.18 points to 15,164.34 at the start of trading. By 0130 GMT the Nikkei had added 1.62 percent.
"Today's move in the Nikkei is largely a result of a more accommodative dollar level," said Daisuke Uno, strategist at Sumitomo Mitsui Banking Corp.
"With Turkey and India raising interest rates and the US Fed set to make its decision on policy soon, markets are still cautious."
The rise marked easing concern over emerging market sell-offs after Turkey's decision on Tuesday to aggressively raise interest rates to defend the lira. India's central bank also hiked interest rates on Tuesday.
Global equity and forex markets have been in turmoil since the end of last week after a plunge in the Argentine peso sparked fresh worries about developing nations' economies.
Investors are focusing on the Fed meeting to see if it announces further cuts to its $75 billion-a-month stimulus, after announcing a $10 billion cut following its last meeting.
A pullback is a plus for the dollar but could exacerbate fears of a capital flight away from emerging markets as dealers look for safer investments.
In Tokyo, the market was boosted by the stronger dollar, which fetched 103.26 yen early Wednesday against 102.97 yen in New York Tuesday afternoon.
The euro also rose to 140.99 yen from 140.73 yen in US trade while it bought $1.3658 against $1.3667.
A weak yen is positive for Japanese exporters as it makes them more competitive abroad and increases their repatriated profits.