Dell says a buyout offer from Southeastern and billionaire investor Carl Icahn is approximately $3.9 billion short of the amount needed to pay shareholders as promised and operate the business.

A special Dell board committee still favors a buyout offer from the struggling PC maker’s CEO and founder, Michael Dell, and investment firm Silver Lake Partners. That bid would take the company private for $24.4 billion, or $13.65 per share.

Southeastern Asset Management Inc., Dell’s biggest independent shareholder, and Icahn teamed in May to pitch an alternative plan that would let Dell shareholders keep their stake in the company and give them either $12 per share in cash or additional shares.

While Icahn and Southeastern’s proposal projects $17.3 billion in liquidity, based on 20 percent of Dell’s shareholders opting for his offer, the company will actually have $13.4 billion, according to the special board committee.

Based on the estimated funding gap, the value of Icahn’s proposed $12-a-share dividend would be reduced to $9.35, or to $8.50 if Icahn and partner Southeastern Asset Management Inc. are the only shareholders to opt for the equity stub instead of cash, the board committee said in a regulatory filing today.

Dell’s committee is pointing out shortcomings in Icahn’s offer to rally support ahead of a shareholder vote next month on Chief Executive Officer Michael Dell and Silver Lake Management LLC’s $24.4 billion buyout. Last week, Dell urged shareholders to vote for the founder’s buyout at a meeting set for July 18. After contacting more than 70 potential strategic and financial buyers during a “go-shop” period, Michael Dell’s offer “is the best alternative available — in a challenging business environment,” Dell said in a May 31 filing.

Dell’s special committee was formed last August after Michael Dell told the board he was considering taking the company private. It said it negotiated six price increases with Michael Dell and Silver Lake. The committee said it also contacted 21 strategic and 52 financial buyers, but a superior offer did not materialize.
Dell and other personal computer makers have seen sales crumble because of the growing popularity of smartphones and tablets. In May Dell posted a 79 percent decline in earnings for the most recent quarter.

Michael Dell believes he can turn the Round Rock, Texas company around by taking it private and diversifying into niches, such as business software, data storage and consulting.
Dell has asked its shareholders to approve the offer from Michael Dell and Silver Lake in a July 18 vote.

The company’s stock added 2 cents to $13.44 in morning trading.

(The Associated Press and Bloomberg News contributed to this report)