U.S. S&P stock futures extended losses to more than 1 percent early on Wednesday after a key gauge of Chinese manufacturing activity slumped to its weakest level in nearly three years.

Chinese factories saw their weakest activity in 32 months in November, a preliminary purchasing managers' survey showed, reviving worries that China may be skidding toward an economic hard landing and compounding global recession fears.

The HSBC flash manufacturing purchasing managers' index (PMI), the earliest indicator of China's industrial activity, slumped in November to 48, a low not seen since March 2009.

The data showed the world's growth engine is not immune to economic troubles abroad, and could further unnerve financial markets already roiled by Europe's deteriorating debt crisis.

November's flash reading is a sharp three-point fall from October's final figure of 51 and indicated Chinese factory output shrank on the month in November. A PMI reading of 50 demarcates expansion from contraction.

The last time the PMI slipped below 50 was in September, when the index hit 49.9.

(Reporting by Masayuki Kitano; Editing by Kim Coghill)

HSBC China