MSCI's broadest index of Asia-Pacific shares outside Japan .MIAPJ0000PUS fell 0.7 percent to its lowest levels in almost two weeks while Japan's Nikkei share average dropped 2.6 percent from a five-month high hit on Tuesday.
That retreat, which came after European shares had suffered their biggest falls since August, stemmed from profit-taking ahead of Friday's U.S. job data, but also reflected worries about the Fed's exit from its asset purchase scheme.
"I think financial markets have already priced in an eventual tapering in the Fed's stimulus. The question is whether the economy can withstand it. The U.S. economy slowed after the end of QE1 and QE2. So one cannot be so sure whether it would be okay this time," said Tohru Yamamoto, chief fixed income strategist at Daiwa Securities.
QE1 and QE2 refer to the Fed's previous episodes of massive asset purchasing, or quantitative easing, the first in 2008-2010 and the second in 2010-11.
Many analysts expect the Fed to begin reducing its latest bond purchases, dubbed QE3, at its March meeting, but some think that could be brought forward to January, or at the extreme, later this month, if the employment data comes in strong.
On Wall Street, the Dow Jones industrial average .DJI fell 0.6 percent while the Standard & Poor's 500 Index .SPX declined 0.32 percent, with consumer discretionary shares .SPLRCD leading the losses amid signs of weak holiday shopping.
While Friday's U.S. jobs report for November is seen as by far the most important, traders will be looking to the ADP employment report, new home sales figures, services activity readings from the Institute for Supply Management, all of which are scheduled for Wednesday.
Solid data on U.S. manufacturing and housing in recent weeks has boosted optimism that the U.S. economy was barely damaged by a government shutdown in October.
The spectre of tapering in the Fed's bond-buying could spook emerging market shares and currencies in particular -- given that they were among the hardest-hit when Fed Chairman Ben Bernanke floated the taper idea back in May.
"Ample liquidity from the Fed had flown to emerging markets, in a way hiding all the problems each market has. But after the Fed signalled tapering in May, investors are focusing on them," said Daisuke Uno, chief strategist at Sumitomo Mitsui Banking Corp.
In Asia, investors' concerns include persistent current account deficits in India and Indonesia, as well as the latest political instability in Thailand.
The Indonesian rupiah weakened 0.8 percent to 11,970 rupiah per dollar, edging near five-year lows hit last week.
The Thai baht held firmer at 32.18 baht per dollar after Thailand's government ordered police to stop confronting protesters, raising hope that days of political violence may end, although the currency still stood not far from a three-month low.
Revived talk of tapering also disrupted the yen's decline, which has been propelled by speculation of more carry-trades on the back of improving risk sentiment.
The dollar fell about one percent to 102.40 yen from Tuesday's six-month high of 103.38 yen.
The euro was steadier at $1.3595, not far from one-month high of $1.3622 hit last week.
The Australian dollar sank 0.7 percent to $0.9072, dangling near three-month low of $0.9055 hit last week, after Australia's July-September gross domestic product growth fell short of market expectations.
Gold and silver, which like stocks have benefited from the U.S. stimulus because of inflation fears, traded near 5-month lows.
Gold last stood at $1,222.74 per ounce near Tuesday's five-month low of $1,215.60 while silver traded at $19.10, having slipped to $18.94 on Tuesday.
But oil prices jumped, with U.S. crude futures hitting five-week high supported by an unexpected drawdown in U.S. petroleum stocks.
Mainland Chinese shares also bucked the regional weakness, with Shanghai hitting a 12-week high .SSEC on high hopes for economic reforms laid out by Beijing.