Palm Inc., said Thursday that it was well on the way to shipping 2 million units of its Centro smartphone, a low-end device whose popularity may be challenged by Apple’s new lower-priced iPhone.

Shares of Palm, a maker of mobile phones and hand-held computers, jumped 9 percent in early trading after the company said Centro would be sold through a third American carrier, Verizon Wireless, starting Friday.

Brodie Keast, senior vice president of marketing, said that Centro’s touchscreen and full keyboard were popular with consumers upgrading from traditional mobile phones.

Asked when the company expects shipments of the Centro to reach 2 million, Mr. Keast said, ”We are confident we will get there in 2008.”

He said 1 million units had been shipped through the end of March.

Centro will now be sold in the United States by Verizon Wireless, Sprint Nextel and AT&T at around $99 or less, depending on retailer discounts. It is also sold through international carriers.

Verizon Wireless is a venture of Verizon Communications and the Vodafone Group.

Apple introduced the iPhone 3G on Monday, slashing the price to $199, just half that of the original model. The move adds a challenge to Palm, since it reduced the price differential between the iPhone and Palm, a CL King & Associates analyst, Lawrence Harris, said in a client note.