As part of the struggling Canadian smartphone maker's strategic review, the RIM board is discussing ways to boost revenue from its new BlackBerry 10 operating system and possibly opening up its proprietary network, the sources said.

At one point, RIM was hoping to add as much as $4 billion in revenue from deals with major telecom carriers, sources said.

"This is a very mature strategy and RIM was very far down the road with a lot of those discussions with carriers," one of the sources added.

The restructuring efforts come as the Blackberry maker tries to stem customer losses to Apple Inc's iPhone and smartphones running Google Inc's Android software.

RIM posted a $125 million loss in its most recent quarter as it wrote down BlackBerry inventories. It took an even larger hit on its underperforming PlayBook tablet computers three months earlier. RIM's stock has plunged 75 percent in the last 12 months, giving the company a market value under $7 billion.

Representatives for Milbank and RIM declined to comment.

A number of investment banks have approached RIM over the past several months, vying for a role as financial adviser. But for now, RIM is not expected to hire a banker unless it decides to sell off a major asset or if the company receives takeover interest from an industry competitor, the sources said.

RIM has worked with Milbank previously and also retains law firm Skadden, Arps, Slate, Meagher & Flom LLP and the consulting firm Monitor Group for strategic advice. The two firms were not immediately available for comment.

Source: Reuters