Mon Sep 1, 2008 12:52am EDT

TOKYO (Reuters) - A sudden slowdown in car sales in China and India is threatening to shrink the global auto market this year, promising tougher times for an industry leaning on the two most populous countries to pick up the slack in the West.

Early this year, industry executives had been optimistic that demand in the world's second- and 11th-largest car markets would charge ahead, despite fallout spreading from the U.S. credit crisis.