BlackBerry announced earlier this week that Fairfax signed a letter of intent that "contemplates" buying BlackBerry for nine dollars (£5.60) a share. Fairfax, BlackBerry's largest shareholder, is trying to attract other investors.
BlackBerry shares lost 6% yesterday, closing a dollar below Fairfax's bid on fears the deal will not happen.
There is no break-up fee should Fairfax walk away, but Fairfax chief executive Prem Watsa said his firm was not in the business of making an offer then walking away or redoing the deal.
"We've got a track record of 28 years of completing what we've done. We've never renegotiated," Mr Watsa said. "We thought long and hard before we offered nine dollars a share and we're not in the business of offering a number and at the last minute changing the figure. Over 28 years our reputation is stellar on that front. We just don't do that."
Mr Watsa stepped down as a board member last month because of potential conflicts when BlackBerry announced it was considering a sale. If the proposed deal goes through, BlackBerry would go private and no longer be traded publicly.
Mr Watsa said Fairfax would not be contributing more to the bid than the 10% it already owned.
"The 10% is like 500 million dollars. It's a significant amount of money," he said. "We're going to bring equity partners and we think the company will be very well capitalised."
He declined to name the other investors he is trying to bring in.
Bernstein analyst Pierre Ferragu said the lack of details made the chances of the deal going through appear grim. He noted that Fairfax was not committing any more equity and said other investors were unlikely to join a bid "that sounds like a last chance rescue attempt for Fairfax's stake".
Fairfax's average cost per share in acquiring BlackBerry shares is 17 dollars (£10.60). The Canadian insurance and investment firm has lost hundreds of millions on BlackBerry.
Analysts say that although BlackBerry's hardware business is not worth anything, the company still owns valuable patents. BlackBerry is also strong in having total cash and investments of about 2.6 billion dollars (£1.6bn), with no debt, though it is burning through that stockpile. In just the past few months, it has spent about half a billion dollars.
Mr Watsa said Fairfax was not buying BlackBerry to break it apart.
"Rest assured when we do this it won't be done to split the company," he said. "I mean one of the reasons I went on the board, and I said it publicly, was to keep the company in Canada and to make sure it survives and exists in Canada. It is one of Canada's most successful companies. Companies do fall on hard times and they come back again and we expect this company to do the same."
Mr Watsa said BlackBerry needed to get out of the media glare that came with being public and work on a long term turnaround in private.
The billionaire founder of Toronto-based Fairfax Financial Holdings is one of Canada's best-known value investors and has taken over troubled companies before. He compared his BlackBerry interest to his stake in the troubled Bank of Ireland. Watsa said his Bank of Ireland stake was now worth double what he paid for it a few years ago at the height of the European crisis.
The tentative BlackBerry deal comes just days after the Canadian company announced plans to shed 40% of its global workforce.
The BlackBerry, pioneered in 1999, was once the dominant smartphone for on-the-go business people and other consumers. But then came a new generation of competing smartphones, starting with Apple's iPhone in 2007. The BlackBerry suddenly looked ancient.
Although BlackBerry was once Canada's most valuable company with a market value of 83 billion dollars (£52bn) in June 2008, the stock has plummeted to eight dollars (£5) from more than 140 dollars (£87.50) a share, giving it a market value of 4.2 billion dollars (£2.6bn), short of Fairfax's offer.