BlackBerry maker Research In Motion Ltd (NASDAQ:BBRY) (TSE:BB) is expected to announced its fourth quarter earnings on Thursday before the bell. And the number of short positions continues to rise as the final moment approaches. Though the international launch of new smartphones Z10 and Q10 has boosted investors’ confidence, short-sellers believe that the turnaround talk is over-hyped.

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Since last month, short interest on the American shares of Research In Motion Ltd (NASDAQ:BBRY) (TSE:BB) has grown more than 13 percent to reach 30.10 percent of the total float. In other words, it rose from 136.5 million shares in the last week of  February to over 155 million shares on March 27, according to FactSet Research Systems Inc. (NYSE:FDS). The upcoming earnings report will give the first official glimpse about the demand of its “make or break” BB10 devices. If the company gives a positive surprise, the accumulating bearish bets would send the stock surging.

Share prices of Research In Motion Ltd (NASDAQ:BBRY) (TSE:BB) have risen over 90 percent in the last six months, but the U.S. launch of its Z10 device was disappointing, according to Goldman Sachs Group, Inc. (NYSE:GS) analysts. BlackBerry’s market share has declined rapidly in the past few years due to rising competition from Apple Inc. (NASDAQ:AAPL) and Samsung Electronics Co., Ltd. (LON:BC94) (KRX:005930) BB10 devices are considered as the struggling Canadian company’s last shot to regain its lost glory.

Though sales in international markets have been encouraging, the U.S. debut of BlackBerry Z10 smartphones was crucial for the company’s success. Analysts expect the company to have sold slightly over 1 million Z10 and Q10 devices in the fourth quarter since their launch on January 31. The exact sale figure will be a key factor in driving the stock after the earnings report. Goldman Sachs Group, Inc. (NYSE:GS) analysts said the lukewarm response in the U.S. market has hampered their confidence in the stock.

When Research In Motion Ltd (NASDAQ:BBRY) (TSE:BB) announced that it has received an order for 1 million devices from an established partner, most people speculated that it was an American telecom carrier. But reports suggest that the order was placed by Brightstar, an Indonesian company.

Research In Motion Ltd (NASDAQ:BBRY) (TSE:BB) shares were up 1.04 percent to $14.61 at 2:12 PM EDT.