UPDATE 1-US FCC approves AT&T's bid for Centennial-sources

* Deal to add 1.1 mln subscribers to AT&T

* Justice Dept approved deal in May with conditions (Adds background)

WASHINGTON, Nov 5 (Reuters) - The U.S. Federal Communications Commission approved AT&T Inc's (T.N) $944 million bid to buy Centennial Communications Corp CYCL.O, two sources familiar with the decision said on Thursday.

The widely expected move comes three weeks after the U.S. Justice Department approved the deal on the condition that AT&T, the No. 2 U.S. wireless provider, sell assets in parts of Louisiana and Mississippi.

AT&T, which was required to sell eight service areas, has reached agreement to sell five of them to Verizon Wireless, a venture of Verizon Communications Inc (VZ.N) and Vodafone Group Plc (VOD.L).

In a bit of a swap, AT&T also agreed in May to buy Alltel Wireless assets that Verizon was required to sell as part of its purchase of Alltel.

Centennial is the 8th largest wireless provider and offers service in six states, Puerto Rico and the U.S. Virgin Islands, the Justice Department said. AT&T estimated Centennial had about 1.1 million wireless subscribers.

The deal was first announced in November 2008 and approved by Centennial stockholders in February.

In an Oct. 22 letter to the FCC, AT&T said it will continue Centennial's roaming agreements for two years and maintain a CDMA network in Puerto Rico and the U.S. Virgin Islands for 18 months. AT&T operates on the alternative GSM network.

AT&T also said in the letter that it would maintain an arms-length distance with America Movil SAB de CV (AMXL.MX) (AMX.N), which is controlled by Mexican billionaire Carlos Slim.

In the United States, Mexico City-based America Movil provides prepaid phone plans under its TracPhone Wireless Inc unit. That service runs on the Verizon Wireless network. (Reporting by John Poirier; Editing by Steve Orlofsky)