Motorola Inc.’s two-year, Razr-fueled resurgence in the global cell-phone market was in trouble Friday after the company warned of disappointing sales and earnings from the key holiday selling season.

Investors sent the company’s stock down sharply amid a consensus that the trendsetting Razr has lost its buzz in the marketplace and that Motorola’s efforts to come up with a new killer product have yet to pay off, hindered by stiffening competition.

Motorola’s pre-announcement Thursday night of worse-than-anticipated fourth-quarter results made it two straight quarters that the company has fallen short of Wall Street expectations. It also threatens to end eight consecutive quarters of market-share gains for a company that, despite improving to a 22 percent share from 16 percent in 2004, remains far short of its goal of recapturing the lead it held in the 1990s from Finland’s Nokia Corp.

Shares fell $1.61, or 7.83 percent, to close at $18.94 on the New York Stock Exchange after sinking as low as $18 earlier in the session, matching their lowest price since July 2004.