A shortage of auto parts stemming from Japan's earthquake may cut global vehicle output by 30 percent within six weeks in a worst-case scenario, research firm IHS Automotive said on Thursday.

This translates to a drop of as many as 100,000 vehicles per day, IHS analyst Michael Robinet said, adding there could be more North American plant shutdowns in the meantime.

We're already feeling the impact in Japan, Robinet said in an interview. North America, Europe, China: those three areas for sure will feel some impact.

Last week, General Motors Co idled its pick-up truck plant in Shreveport, Louisiana. Toyota Motor Co <7203.T> is likely to idle its own pickup truck plant south of San Antonio.

The delivery of parts from transmissions to electronics to semiconductors is being hampered by the Japanese earthquake and subsequent infrastructure problems. About 13 percent of the global auto industry output has been lost now because of parts shortages, Robinet said.

The slowdowns could grow even more severe by the third week of April. To cope, automakers will likely funnel parts to their higher margin vehicles or new product launches. The pick-ups built at the GM and Toyota plants were low-sellers.

Robinet stressed that situation remained difficult to predict. I've never seen a situation so fluid, he said.

(Reporting by Deepa Seetharaman; Editing by Steve Orlofsky)

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