Asian stock markets struggled on Wednesday as weaker U.S. data damped down recent optimism that the world's largest economy may escape the gloom from the euro zone debt crisis, while Chinese manufacturing surveys failed to break the cautious mood.

MSCI's broadest index of Asia-Pacific shares outside Japan was down 0.3 percent at 0300 GMT, after spending the first few hours of trading swinging between positive and negative territory.

The index ended January up nearly 10 percent for its best showing in three months.

Japan's Nikkei average bucked the regional trending, rising 0.3 percent despit opening down, as fund managers took the view that Japanese stocks remain undervalued.

Investors were on their guard ahead of more manufacturing surveys later from the world's biggest economies.

Data from China failed to give markets a decisive lead. Shares strengthened after the official Purchasing Managers' Index showed the manufacturing sector expanded modestly in January, with the index reading inching up to 50.5 from 50.3 in December, above a 49.5 reading forecast.

But the rise petered out after the release of a separate private sector survey later. The HSBC final PMI stood at 48.8 in January, a reading signalling contraction albeit at the slowest pace in three months.

A reading falling short of expectations in China's official PMI could have fuelled concerns that policy makers in the world's second-largest economy were not taking sufficient measures to spur growth and weighed on commodities-linked currencies by stoking worries about weakening demand.

"The data merely highlights lacklustre growth, as Asia is the main exporter to Europe, and it will only become clearer that the European debt woes are having an impact on the real economy around the world," said Takao Hattori, senior investment strategist at Mitsubishi UFJ Morgan Stanley Securities in Tokyo.

"The probability of the euro zone debt problems turning into a global financial crisis has receded considerably and the risk of global growth grinding to a halt is low, but that doesn't change the main scenario for an economic slowdown generally."

KOREAN EXPORTS DOWN

Earlier data from South Korea showed its exports to the European Union for the Jan. 1-20 period fell 44.8 percent from a year earlier, while preliminary trade data showed the country's exports fell 6.6 percent in January from a year earlier, against a rise of 0.7 percent forecast.

Global manufacturing surveys due later this session include the euro zone and the Institute for Supply Management index from the United States. The euro zone flash inflation for January and U.S. January employment data from ADP are also due.

The reports were likely to show many economies are seeing a sluggish start in 2012 amid slowing demand, putting central banks around the world under pressure to keep an accommodative policy to support growth.

"Inflation is likely to ease further in the months ahead, giving central banks room to cut. With cuts priced in, demand-supply dynamics are more useful in gauging direction," said Standard Chartered in a research note.

U.S. stocks were undermined on Tuesday after U.S. home prices and business activity in the U.S. Midwest missed expectations and consumer confidence fell unexpectedly.

BONDS FIRM

The dollar stood around 76.14 yen, matching a three-month low touched on Tuesday. The euro slipped as no concrete progress was made in the debt restructuring negotiations between the Greek government and its private bond holders. The single currency was off 0.2 percent to $1.3066. The Australian dollar rose as high as $1.0638 before slipping to $1.0610.

Athens struggled to convince foreign lenders it could bridge a funding shortfall with reforms. A senior Greek banker said the crucial debt swap deal to avoid a default is largely in place, but a final accord hinged on Athens showing its determination to pursue tough measures.

Portugal, which has come under fire from markets recently, said it has no intention of asking for more funding or extending its 78-billion-euro bailout, knowing its debt payments are covered for at least a year. Lisbon has a far lighter calendar than Athens with just one payment due this year.

Portuguese government bond yields took a respite from a recent surge, with the 10-year yields falling to 16.49 percent from above 17 percent.

Italy and Spain, the other highly indebted euro zone countries only recently at the centre of market jitters over their refinancing, are also seeing their debt yields move away from peaks seen as unsustainable for the economy.

The 30-year Japanese government bond yield dropped to a four-month low of 1.890 percent on Wednesday.

"With credit risks still simmering, government bonds of industrialised countries will likely continue to attract investors," Hattori said.

Asian credit markets were subdued, with spreads on the iTraxx Asia ex-Japan investment grade index narrowing by a couple of basis points.