Toronto, Jul 12 (IANS): As BlackBerry maker Research In Motion (RIM) co-CEOs face jittery investors Tuesday at the annual meeting amid the company's declining market share, Apple has stepped up efforts to steal BlackBerry's corporate client base.

Corporate executives and leaders favour BlackBerry because of its security encryption.

But the onslaught from Apple's iPhone and Google Android devices has pushed BlackBerry from the top to the third slot in the US smart phone market in a matter of months.

As the Canadian wireless giant struggles to replace its aging handsets, Apple has taken aim at its enterprise base by targeting them with a back-page ad in The Economist.

The ad highlights Apple's apps for business uses. Compared to App Store which offers more than 425,000 apps, BlackBerry's App World has just 37,000 apps.

Claiming that 88 per cent of Fortune 500 companies are now using iPhones and 75 per cent iPads, Apple has also launched a new website to help companies integrate the iPhone in their information systems.

All this is not good news for the BlackBerry company which is fast losing its share in the US smart phone market.

From being the top-seller with a market share of more than 33.5 percent in October, it has now tumbled to the third position at 24.7 percent. It stock has sunk more than 50 percent this year, currently hovering about $27 - the lowest level in five years.

Its fortunes have sunk to just $14 billion from $83 billion in June 2008. With Apple and Microsoft sitting on cash piles of more than $40 billion each, there has been speculation that the either of them could buy out the BlackBerry company.

But the two co-CEOs - Mike Lazaridis and Jim Balsillie, who control management and board chairmanship, have been reluctant to loosen their grip on the company.

Though they have managed to ward off a vote on giving independence to the board from management, Tuesday's annual meeting is going to be stormy as investors seek a fresh direction for RIM.