MSCI's broadest index of Asia-Pacific shares outside Japan lost 0.2 per cent, with relief over a perceived ebb in Ukrainian tensions replaced by caution over the Fed's policy review. Tokyo's Nikkei stock average fell 0.4 per cent.
The Fed is widely expected to continue to reduce the size of its monthly bond purchase program by $10 billion each meeting, but also to alter its forward guidance when it delivers the policy statement on Wednesday, the first policy review to be presided over by new Fed Chair Janet Yellen.
"What will also get a lot of attention is the winter that the United States has just suffered. Some commentators are looking for evidence of recognition from the FOMC that the winter has altered their guidance on the economic recovery -as tapering has been explicitly based on data.
On Tuesday, U.S. stocks climbed for a second straight session, with the S&P 500 in striking distance of its record after comments from Russian President Vladimir Putin that he did not plan to seize other regions of Ukraine were taken as a signal that the crisis may not deepen for now.
But in a reminder that the situation in the former Soviet republics was still volatile, oil prices rose following a report that a Ukrainian serviceman was killed after his base in Crimea came under attack.
Brent crude oil traded at $106.60 per barrel after touching a six-week trough of $105.85 the previous day.
Going forward, impact on investor risk appetite will depend on whether the crisis turns into a regional issue from a global one. That in turn will hinge on sanctions the European Union and United States impose on Russia, particularly in the energy arena..
The euro stood little changed, with a recent rise in U.S. Treasury yields slightly denting its appeal relative to the dollar and preventing the common currency from extending its 2-1/2-year high of $1.3967 hit last week.
The euro was last steady $1.3925, and against the Japanese yen it was fetching 141.16 yen, largely steady from late New York levels.
The dollar was down about 0.1 per cent on the day at 101.36 yen. The yen showed little reaction to Japan's larger-than-expected trade deficit.
The 10-year U.S. Treasury note yielded 2.670 per cent, having pulled away from a recent trough of 2.610 per cent hit last Friday.
China's yuan traded more than 1 percent beyond the midpoint set by the central bank, the first time it has traded by such a margin after the daily trading band was widened to 2 percent.
The yuan opened at 6.1940 per dollar, 20 pips weaker than Tuesday's close of 6.1920. It went as low as 6.1986, an 11-month trough.
A rebound in risk appetite continued to dampen demand for gold. Spot gold was at $1,357.56 an ounce, having slipped from a six-month high of $1,391.76 hit on Monday.
Copper edged up ahead of the Fed's monetary policy meeting later, although persistent worries over growth and credit markets in top-user China capped prices.
Three-month copper on the London Metal Exchange had climbed 0.1 per cent to $6,488 a tonne, extending gains from the previous session.