Sprint Nextel will offer a smartphone powered by the Google-backed Android operating system by the end of the year, according to comments by CEO Dan Hesse.

The third-largest U.S. carrier is already a member of the Open Handset Alliance, but Hesse said last year the Linux-based OS wasn't "good enough to put the Sprint brand on it." Since that time, the open-source mobile OS has received major software updates, and it appears to be up to Hesse's standards now.

"The reviews say now it's ready for prime time," Hesse said of Android at the Fortune Brainstorm Tech conference. "It wasn't when it first came out."

A flagship Android handset, along with high-end devices like the Palm Pre and the BlackBerry Tour, could help Sprint retain subscribers who flee to AT&T and Verizon Wireless for exclusive smartphones like the iPhone and BlackBerry Storm. Hesse did not say which cell-phone maker would provide Sprint's Android phone, but he did say he was "impressed" with what he has seen from Motorola.

The move is another sign that the Linux-based OS is picking up some steam, and Google said it expects up to 20 handsets to be released by the end of the year. Because it is a free OS, some of these handsets will be from relatively unknown manufacturers, but Android has drawn interest from top-five cell phone makers like Samsung, Motorola, and Sony Ericsson.

The mobile operators have also given Android more attention, as Sprint and Verizon are expected to have handsets out within six months or so. T-Mobile was the first U.S. carrier to offer an Android smartphone, and it plans to go "deeper, further, and faster" with the OS in order to stand out from the competition.

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