It's looking increasingly as if AT&T will give Verizon a run for its money to be the first Tier 1 operator to launch voice-over-LTE (VoLTE) service in the US, as rumors of testing on Samsung devices leak out.

AT&T Inc. (NYSE: T) announced its first VoLTE-capable smartphone, the Padfone X, at CES last week. Surprisingly, it didn't come from a top-five smartphone vendor, but from AsusTek Computer Inc. The Padfone X will support both HD voice and VoLTE, although AT&T isn't saying what that launch date will be nor if it will turn on that support at launch. (See AT&T Hears Call of VoLTE in 2014.)

At the same time, a report in the Korea Herald Monday suggests the carrier is testing the 4G voice service on Samsung Corp. smartphones. The report didn't indicate which Samsung phones are in use, but Galaxy Note 3s have been spotted on Verizon Wireless 's LTE network as well. (See Verizon VoLTE Testing Spotted.)

Samsung as a test partner would make a lot of sense for AT&T because the CE giant already has VoLTE handsets fired up in South Korea with SK Telecom (Nasdaq: SKM) and LG Telecom . Plus, long-time AT&T partner Apple Inc. (Nasdaq: AAPL) hasn't announced any plans to support 4G voice, although its latest devices do support HD voice. (See South Korea Hears First 4G Voice Service.)

With testing in full swing and PR increasing, AT&T and Verizon are neck-and-neck on getting service commercially launched. Neither one has been in a hurry -- they've been talking about VoLTE for years now. But with VoLTE smartphones coming soon, both rumored and confirmed, it's looking more likely that a commercial launch is imminent in the US. (See VoLTE Needs Passing Grade From Operator Tests.)

That's no guarantee the service will wow users, but at least we'll soon get to find out. (See Can You Hear the Voice?)

— Sarah Reedy, Senior Editor, Light Reading