General Motors may sell shares for as much as $33 in an initial public offering, 14 percent more than originally planned, said people familiar with the matter.

The automaker majority owned by Uncle Sam said Nov. 3 that it may raise as much as $10.6 billion by selling 365 million shares for as much as $29 each.

Increasing vehicle sales and earnings at GM along with a surging equity market have boosted demand for the stock, prompting the company and its banks to encourage adding shares or raising the price range, the people said.

GM will sell $4 billion worth of preferred stock, up from $3 billion, said one person, who asked not to be identified because the plans are private. Demand was so strong that GM and the Treasury also discussed increasing the number of shares offered, sources said.

At $33, GM would raise $12 billion selling common stock. Including an overallotment option for the underwriters to sell more shares, the offering would raise $13.9 billion.

JPMorgan Chase and Morgan Stanley, which are among GM’s lead investment banks, have urged the Treasury to offer more shares than the 419.8 million that would be sold if the current overallotment option is exercised, a source said.

The price probably will be $32 to $33, though that hasn’t been determined, said one person, who asked not to be identified because the discussions are private. An amended registration statement is expected to be filed with the Securities and Exchange Commission today, the person said.

GM is seeking to sell as many shares as possible to reduce the government’s stake, and the automaker’s banks want a larger offering to increase the fees they’ll earn, said Maryann Keller, founder of a self-named consulting firm in Stamford, Conn.