NEW YORK (AP) — Shares of Motorola slid Thursday after Goldman Sachs cut the company's rating to "Neutral" from "Buy," citing a climb in the company's share price since late January.

In a note to investors, Goldman analyst Simona Jankowski said the "initial thesis was that the market was undervaluing Motorola's handset business, with the stock implying a negative $5 (billion) value" in January.

Motorola stock is up more than 50 percent since Goldman assigned the company a "Buy" rating Jan. 20.

"We believe the market is now pricing in our view that the handset business should at least have a small positive value given potential break-even next year," Jankowski said.

Motorola's cell phone business posted an operating loss of $509 million for the first three months of the year, though that was narrowed from a loss of $595 million the quarter before.

Jankowski acknowledged there is some risk that the downgrade could prove unwarranted if Motorola's new smartphones are more successful than expected.

Part of the unit's turnaround plan is a new set of phones based on Google’s Android operating system due out in the fourth quarter. But the analyst said the risk of success or failure is fairly priced into the stock.

Shares fell 34 cents, or 5.1 percent, to $6.27 in afternoon trading. The stock is up about 38 percent year-to-date.