U.S. mobile carrier AT&T Inc. is using Samsung's smartphones to test-run the voice over long-term evolution (VoLTE) service slated to be launched this year, industry sources said Monday.

AT&T included Samsung's Galaxy smartphones among the devices to be tested for the VoLTE service, the sources said, a move expected to open ways for the South Korean player to expand its foothold there.

The VoLTE service, which offers voice calls through the fourth-generation LTE network, enables clearer quality and faster connection than services on the existing 3G network. Previously, LTE networks supported only data transmission.

Verizon Wireless, the top mobile carrier in the U.S., currently has no plans to commence the VoLTE service, and Apple's smartphones also do not support the latest voice network.

Samsung Electronics Co. released its VoLTE smartphones in its home turf in August 2012, in conjunction with commercialized VoLTE services by local mobile carriers SK Telecom Co. and LG Uplus Corp.

Market watchers said AT&T's latest move will lend support to Samsung's expansion in the U.S. market as it has been competing neck-and-neck with Apple, with the U.S. firm having a slight upper hand. (Yonhap News)