DALLAS - Dell Inc. is making a late push to win shareholder support for founder Michael Dell's plan to take the slumping computer maker private, an indication that Thursday's scheduled vote could be close.

Supporters of the $24.4 billion buyout offer believe Dell Inc. stands a better chance of turning around if it can make long-term strategic decisions without worrying about meeting Wall Street's quarter-to-quarter expectations. But some big investors have already signaled opposition to the bid. Investor Carl Icahn believes the offer undervalues the company.

Dell's decision to go private comes at a time when more people are spending their money on smartphones and tablets and PC sales have been falling. Tablets are expected to outsell laptop computers this year.

CEO Michael Dell is hoping to evolve the company into a more diversified seller of technology services, business software and high-end computers -- much the way IBM was successfully transformed in the 1990s.

Shareholders have until Thursday's meeting at the company's headquarters in Round Rock, Texas, to cast votes.

On Tuesday, a special committee of the company's board sent a letter to shareholders emphasizing its opposition to a rival plan by Icahn and his Southeastern Asset Management fund. Together, they own 13 percent of Dell.

The committee said Icahn could have trumped the $13.65-per-share offer from Michael Dell and his group of investors, but instead submitted a recapitalization plan that it called risky and short on details.

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"I believe it's a very, very close vote," said Patrick Moorhead, a technology analyst in Austin, Texas. "Institutional investors usually let a company know where they stand, so you can imagine a war room where [Dell advisers] are counting votes."

In corporate elections, shareholders can change their vote right up to the last minute. Michael Dell's task is made more difficult by an agreement that he would not cast his shares, which represent about 16 percent of the company's stock. That means the board needs slightly more than 42 percent, or a majority of the remaining shares, to get the deal done.