The benchmark Nikkei 225 index, which rose 1.53 percent on Tuesday, lost 136.27 points to 13,733.55 at the start.

The Fed is to wrap up a two-day policy meeting Wednesday with market players looking for clues to its thinking on winding down its massive stimulus programme.

Investors are also waiting for data on April-June gross domestic product to see how the world's largest economy is faring.

Currency rates were static. The dollar was at 98.00 yen in early Asian trade Wednesday, hardly changed from 98.02 yen in New York Tuesday afternoon.

The euro fetched $1.3259 and 130.04 yen compared with $1.3264 and 130.02 yen. New York stocks closed mostly flat on Tuesday. The Dow Jones Industrial Average slipped 0.01 percent to 15,520.59.