* Asian manufacturing PMI's point to waning activity
* China holds steady, but Japan, India and South Korea slow
* Subsiding inflation becoming a concern as commodities slide
By Wayne Cole
SYDNEY, Oct 1 (Reuters) - Factory activity stumbled across much of Asia in September, with slowdowns in India, Japan and Taiwan and an outright decline in South Korea delivering a setback to hopes for a pick in world growth this year.
The lacklustre performance helped lift the U.S. dollar above 110.00 yen for the first time since mid-2008 while punishing commodity prices globally, a positive for consumers but also a force for disinflation.
Indeed, subsiding price pressures was a feature of many of the manufacturing surveys out on Wednesday. Even Taiwan, one of the stronger economies in the region, reported output prices were cut for the eighth month in a row, while input inflation was the lowest in over a year.
"This should give the authorities plenty of room to keep policy accommodative to support growth," said HSBC economist, John Zhu, a conclusion that goes for plenty of other countries.
China this week cut mortgage rates and downpayment levels for some home buyers for the first time since the global financial crisis, escalating efforts to boost an economy threatened by the sagging housing market.
Beijing has for some time now found it can no longer rely on exports and manufacturing as an engine for growth.
The official Purchasing Managers' Index (PMI) of activity stayed stuck at 51.1 in September, only modestly above the 50 level that separates growth from contraction.
"The economy still faces a degree of downward pressure," said Chen Zhongtao, an official at the China Federation of Logistics and Purchasing which helps to publish the PMI.
International investors have also been unsettled by reading pro-democracy protests in Hong Kong, watchful for any signs of fallout for China's economy.
In Japan, the economy is still struggling to get over a hike in the sale taxes that took effect five months ago.
The final Markit/JMMA Japan PMI eased to 51.7 in September, from 52.2 in August, and followed data showing industrial output, consumer spending and real wages all fell in August.
There was a glint of light as the Bank of Japan's closely watched survey of business confidence improved for the first time in two quarters. Yet sentiment for the services sector still worsened.
All of which did little to relieve pressure on policymakers to expand stimulus ahead of Prime Minister Shinzo Abe's decision by year-end on whether to proceed with a second tax hike.
Taiwan's version of the PMI cooled to 53.3 in September, from a robust 56.1 the month before. The country's manufacturers have been riding a wave of popularity for Apple new iPhones but growth in new orders and new exports still slowed in the month.
Indian factory activity expanded at its slowest pace in nine months in September with an index reading of 51.0, down from 52.4 in August, breaking what had been a promising run.
Faring even worse was South Korea, where the HSBC/Markit PMI slid to a three-month trough of 48.8 in September, indicating activity contracted.
Separate official figures showed South Korea's exports to China rebounded in September, while annual growth in exports to the United States reached almost 20 percent. Shipments fell over 5 percent to European Union, underscoring its role as an albatross around the neck of global trade.
With so much of manufacturing struggling, worries about demand have plagued oil and commodities in general. World oil prices tumbled to their lowest in more than two years this week, iron ore a five-year trough and copper a four-month low.
The weakness engulfed food as well. Corn prices fell to a five-year low on Wednesday, while soybeans were near the lowest since early 2010 and wheat not far from a four-year trough amid plentiful world supplies.
While falling commodity prices are a boon to consumer spending power in much of the world, it comes at a time when inflation is already ominously low in many developed nations.
Euro zone inflation matched a record low of 0.7 percent in September, piling pressure on the European Central Bank to do more to revive the economy at its policy meeting later Thursday.
Japan is fighting to stop inflation from receding despite a record-breaking asset-buying campaign by the central bank.
Inflation in South Korea slowed to a seven-month low of 1.1 percent in September, far below forecasts and a trigger for markets to price in another rate cut there. (Editing by Kim Coghill)