Research In Motion slashed its earnings outlook for the current quarter by 11 percent on Thursday, saying it expects to ship fewer and cheaper BlackBerry smartphones.

In an unusual warning just a month after it disappointed investors with a weak short-term outlook, RIM said it expects diluted earnings between $1.30 and $1.37 a share for the period to the end of May, down from the $1.47-$1.55 range it forecast in late March. Its stock slumped 12 percent in extended trade.

This is the beginning of the slide, said Edward Snyder from Charter Equity Research. It's going to be like air coming out of a balloon slowly.

RIM said the shortfall was mainly due to slower shipments of its BlackBerry smartphones and an increasing reliance on sales of its cheaper devices.

Shipments would likely be at the low end of the 13.5-14.5 million forecast it gave in March.

But RIM maintained its robust forecast for full-year earnings of $7.50 per share.

It said it would make up the shortfall in the second half with new product launches and cost cutting.

The Canadian company said it has not experienced significant supply disruptions from the Japan earthquake and shipments of its new PlayBook tablet are on track.

(Reporting by Alastair Sharp; editing by Janet Guttsman)

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