(Reuters) -- Asian shares fell for a third day in a row Wednesday as investors grew more risk-averse, with renewed uncertainty over Greece's bailout and mounting worries about slowing global economies overshadowing support provided by ample liquidity.

The three U.S. equity indexes recorded their biggest one-day percentage drop this year on Tuesday while the CBOE Volatility index VIX <.VIX> rose to reflect receding risk appetite.

Commodity currencies such as the Australian dollar fell for a second session in Asia, while the euro also stayed vulnerable.

Asian credit markets weakened in tandem with riskier assets, pushing the spread on the iTraxx Asia ex-Japan investment-grade index 5 basis points wider early on Wednesday.

The MSCI Asia Pacific ex-Japan index <.MIAPJ0000PUS> fell 0.2 percent, while Japan's Nikkei average <.N225> opened down 1.3 percent.

The correction likely reflects concerns about the Greek PSI (private sector involvement), Chinese growth and high oil prices. But these concerns are not new, and so far, they are more likely to reflect profit taking than a fundamentally driven re-pricing of risk, Barclays Capital analysts said.

The current sell-off in risky assets may have more room to go, but it is already opening up interesting short-term investment opportunities in G10 FX, they said.

Athens turned up the heat on its creditors on Tuesday as it sought to secure a bond swap that will cut its mountainous debt, while the main bondholders group warned a disorderly default would cause over a trillion euros of damage to the euro zone.

Some Greek pension funds and foreign investors rejected the offer which will see investors lose almost three-quarters of the value of their holdings.

Greek private creditors have until Thursday night to say whether they will participate in a bond swap that is a crucial part of a bailout programme to save Greece from bankruptcy and meet a debt repayment on March 20.

More signs emerged of the damage to growth inflicted by the euro zone debt crisis, as Brazil followed China in raising fears of slowing growth, with data on Tuesday showing South America's largest economy expanded just 2.7 percent in 2011 after surging 7.5 percent in 2010.

The euro zone also faced prospects of a full-fledged recession as the European Union said on Tuesday the euro zone's economy in the final months of 2011 was hit by a collapse in household spending, exports and manufacturing.

The euro was little changed at $1.3119, recovering from a three-week low of $1.3103 touched on Tuesday. The Australian dollar hovered near a six-week low around $1.0525 hit the day before.

The VIX index, which measures expected volatility in the Standard & Poor's 500 index <.SPX> over the next 30 days, on Tuesday rose almost 16 percent, the biggest one-day rise since November, as the S&P 500 .SPX benchmark marked its worst three-day period since December.

Oil prices retreated on Tuesday as data showing a shrinking euro zone economy fueled fears of curbed demand for petroleum, while news that major powers accepted Iran's offer for more talks on its nuclear program eased concerns about supply disruptions.

Brent crude delivery settled down 1.47 percent at $121.98 a barrel on Tuesday. U.S. crude was up 0.3 percent at $104.96 a barrel on Wednesday, after settling off 1.89 percent at $104.70 a barrel.

(Editing by Michael Perry)