The Fed ends a two-day policy meeting on Thursday at which many economists expect the US central bank will launch a third round of bond purchases to drive down borrowing costs and spur a stronger recovery.

"Whether they (the US Fed) come out with a new programme or extend in some older programmes or decide whether to leave rates on hold is a really big thing for the market," said Juliana Roadley, a market analyst at Commonwealth Securities.

"That's why the market's nervous. There's no true indication on why the market should be selling off today but they're all a bit quiet ahead of that. I think major investors just don't want to get in ahead of this major announcement.

The benchmark S&P/ASX 200 index was down 14.2 points at 4,347.1 as of 0221 GMT.

Westpac Banking Corp dropped 0.5 percent, leading losses among banks.

The market remained soft despite a top German court giving conditional approval overnight for a rescue fund to aid the euro zone's sovereign debt crisis.

Germany's Constitutional Court gave the green light on Wednesday for the country to ratify the euro zone's new bailout fund and budget pact, but insisted the German parliament have veto powers over any future increases in the size of the fund.

New Zealand's benchmark NZX 50 index fell 0.2 percent to 3,783.5 points.

STOCKS ON THE MOVE

* Myer Holdings Ltd, Australia's largest department store chain, briefly tumbled to a six-week low after the company reported a smaller-than-expected fall in second-half profit but gave no earnings guidance, citing an uncertain outlook in a tough retailing environment.

The stock pared losses and last traded down 0.4 percent at A$1.84.