Research In Motion Ltd., the maker of BlackBerry smart phones, forecast second-quarter profit and sales that may fall short of analysts’ estimates, causing the shares to slip 6 percent in extended trading.

The Waterloo, Ont.-based RIM reported earnings of $643 million or $1.12 a share in the quarter on revenue of $3.42 billion, compared with $482.5 million or 84 cents on revenue of $2.24 billion a year earlier.

Analysts on average estimate profit of 98 cents and sales of $3.61 billion.

Revenue was up 54 percent from the $2.24-billion earned in the same period a year ago.

RIM added 3.8 million new BlackBerry subscriber accounts during the quarter, just slightly below the 3.9 million new accounts added in the previous quarter.

RIM fell $3.97 to $72.58 in late trading after closing down at $76.55 at 4 p.m. New York time in Nasdaq Stock Market trading. The shares have climbed 89 percent this year.

Looking ahead into the current quarter, which has already seen the launch of the Palm Pre and Friday will see the launch of the iPhone 3G S, RIM plans to release its new phone, the Tour, this summer. The new handset uses third-generation networks to operate globally and features the sharpest resolution of any BlackBerry yet.

RIM said it expects revenue between $3.45 billion and $3.7 billion. Meanwhile, earnings per share should fall between 97 cents and $1.03. Analysts were looking for $3.61 billion in revenue and earnings per share of 97 cents.