Global markets have been filled with doubt this week over whether the U.S. Federal Reserve and the European Central Bank, meeting later on Wednesday and Thursday respectively, will or can do enough to lift the world economy.

Although the Fed's forecasts of 1.9-2.4 percent growth for the U.S. economy this year look increasingly unrealistic, the central bank is expected to leave interest rates steady when it meets later, and there is uncertainty over what the ECB can do to ease the protracted debt crisis.

Disappointment over sentiment surveys in China added to the engulfing gloom for investors.

China's official factory purchasing managers' index fell to an eight-month low of 50.1 in July from 50.2 in June.

At least the overall index held the right side of 50, the line dividing expansion from contraction, thanks to an output sub-index that suffered only a slight slip to 51.8 from 52.0.

"This is not the bump that the authorities are looking for. But, the good news is that things are not getting significantly worse," IHS Global Insight economists told clients in a note.

The HSBC China PMI, also published on Wednesday, rose to a seasonally adjusted 49.3, its highest level since February, but July marked the ninth straight month that the private-sector PMI was below 50, indicating contraction.

Analysts drew some comfort from the slight improvement in the HSBC PMI, which focuses on smaller private enterprises in contrast to the official PMI that primarily covers the big state companies.

"The Chinese manufacturing data clearly highlights the soft landing that is taking place across mainland China. The low inflation environment should allow Chinese authorities to provide further stimulus in coming months," said Craig James, economist at Commsec in Sydney.

But the good news pretty well stopped there, with 10 of China's 11 major sub-indexes in the official PMI locked under 50, showing just how much the economy is struggling to revive its momentum, with little evidence of measures aimed at boosting domestic demand taking quick effect.

The weakness of new export orders, at 46.6 in China official PMI, was a common trait in Asia.

Manufacturing activity in South Korea shrank the most in seven months, according to a HSBC/Markit survey, with the purchasing managers' index dropping to 47.2.

South Korea's new export orders at 48.59 in July were slightly better than in June, but hardly heartening, while Taiwan's fell at their fastest pace since December.

As if to underscore the gloom for exporters, official Korean data on Wednesday showed exports in July fell the most in nearly three years.

Korea also released data on Tuesday showing industrial output fell four times more than expected, and Taiwan lopped a full percentage point off its forecast for economic growth this year.

Those findings reinforced the message of a PMI survey released in Japan on Tuesday, which showed the factory sector shrinking at its fastest pace since last year's earthquake.

The slump reflects, in large degree, the sad state of Asia's European and American customers, though falling import demand in China was a factor for some.

The manufacturing PMI for the euro zone due to be released later on Wednesday is expected to show the region locked deep in a contractionary phase, with a Reuters poll forecasting an index at 44.1 for July.

In the United States, the Institute of Supply Management is expected to report later on Wednesday that its gauge popped back up above 50 in July after slipping to 49.7 in June on a slump in new orders.

In a further worrying sign for Asia, PMI employment sub-indexes in China, South Korea and Taiwan all pointed to contraction. So far in the current downturn, Asia has yet to see a repeat of the heavy job losses suffered in the 2008/09 global crisis.

The coming months are a sensitive time for China with a leadership succession looming later this year for the ruling Communist Party.

President Hu Jintao was quoted on Tuesday saying fiscal and monetary policy support for the economy would be stepped up in the second half, while Premier Wen Jiabao spoke of policy fine tuning and signs that the economy was stabilizing, after growth slowed to its slowest pace in more than three years in the second quarter.

India, Asia's third-largest economy, is saddled with multiple problems, including the growing probability of a drought wrecking the farm sector, and factories grinding to a halt amid a spate of wide scale power outages.

The situation has not been helped by doubts over the Indian government's ability to push through reforms, while its central bank has ignored calls for interest rate cuts, saying that the government needs to reduce its fiscal deficit first.

Those worries were all clearly manifest in a survey that showed shrinking export orders and sluggish output reduced manufacturing growth to its slowest pace since November.

The HSBC manufacturing PMI fell to 52.9 in July from 55.0 in June, its biggest one-month drop since September last year.

Like elsewhere, new export orders formed a black spot, slumping to 49.7 in July from 52.3 in June.

A top policy adviser to the government on Tuesday raised the probability that growth this fiscal year will match or fall below the 6.5 percent growth in 2011/12 -- its slowest rate of growth in nine years.

(Additional reporting by Reuters bureaus in Beijing, Seoul, Bangalore and Taipei; Writing by Simon Cameron-Moore; Editing by Neil Fullick)

• A Permanent Economic Emergency