Toronto, Apr 22 (IANS): The BlackBerry maker Research In Motion (RIM), which is pinning hopes on its PlayBook tablet to be a game-changer for the Canadian wireless giant, is banking on Verizon and AT&T to boost its sales.

Cellular carriers in the US and Canada serve not only as service providers but also as retail stores for mobile devices for smart phone makers.

According to a report here, the BlackBerry tablet will be sold at about 20,000 such stores in Canada and the US - twice the number that offer Apple's iPads because of RIM's old relationships with carriers. Apple entered the smart phone market only in 2007 when the BlackBerry smart phone was the king.

But North America's two largest wireless companies have not yet said when they will start selling the PlayBook, which sold about 50,000 units on the opening day Tuesday.

Verizon, which Thursday reported strong quarterly results on surging iPhone sales, didn't say during its post-results conference call with analysts whether it will offer the BlackBerry tablet soon.

Verizon, which has the world's largest number of BlackBerry users, says it has still to evaluate the Blackberry tablet.

According to Verizon spokesman Marquett Smith, "once testing (of the PlayBook) is complete, we will evaluate the product's viability when compared with the rest of our lineup".

But it is unusual for a wireless carrier to express its indecision so publicly, further fuelling the perception that the PlayBook may have been rushed to market, says the Globe and Mail.

Analysts say RIM rushed the tablet into the market and gave Verizon and At&T little time to evaluate it beforehand. But since this first-generation PlayBook is only Wi-Fi, it needs no cellular network connectivity.

So till the promised cellular-ready, 3G version of the tablet comes out in summer, all that current PlayBook users need is a Wi-Fi spot or tether their tablet to their BlackBerry smart phone via BlackBerry Bridge software, without buying new data plan.

It is not known whether Verizon or AT&T will support BlackBerry Bridge.

But RIM needs the two giant US carriers soon on board to boost initial tablet sales in North America.