Blackstone Group LP submitted a bid for the assets Verizon Wireless plans to spin off as a result of its acquisition of Alltel Corp. (AT), according to a source familiar with the deal.

Blackstone joins a group of bidders already in play. The assets represent the $3 billion in wireless assets that Verizon Wireless is mandated to sell to ease antitrust concerns.

In February, The Wall Street Journal reported that rival AT&T Inc. (T) made a bid for the assets, while Carlyle Group and Kohlberg Kravis & Roberts & Co. made a joint bid.

Some industry observers believe AT&T will end up the winner since it's the most logical acquirer.

Verizon Wireless spokesman James Gerace declined to comment, as did AT&T spokesman Michael Coe. A Carlyle spokesman also declined to comment. Spokesmen for Blackstone and KKR weren't immediately available for comment.

Verizon Wireless - jointly owned by Vodafone Group Plc (VOD) and Verizon Communications Inc. (VZ) - became the nation's largest wireless carrier with the $28 billion Alltel deal, which closed in January.

Verizon Wireless added 12.9 million Alltel customers to its own base of 72.1 million subscribers.

Verizon shares fell 2.4% to $31.80 in late trading Tuesday, and Vodafone fell 3.1% to $18.18, while AT&T shares fell 2.3% to $25.58.

-By Roger Cheng, Dow Jones Newswires; 201-938-2020; roger.cheng@dowjones.com