T-Mobile US executives blasted AT&T’s ambitious 5G plans this week, citing numerous unanswered questions around device availability, spectrum and footprint.

AT&T announced plans to launch mobile 5G by the end of 2018. However, the company’s release left out specifics including what markets will be included in the launch and what devices will be compatible with the new capabilities. The latter is a particularly pertinent question as most major chipset vendors – including Qualcomm and Intel – said they expect commercial 5G chipsets to become available in 2019.

T-Mobile CTO Neville Ray was quick to point out these omissions: in a video posted on Twitter he reiterated “everything we see supports mobile form factor chipsets, primarily from Qualcomm and maybe from Samsung, in the first half of 2019”. Qualcomm UK followed up with its own tweet noting the company “can’t wait for the first commercial 5G NR smartphone in 2019”.

An AT&T representative told Mobile World Live (MWL) only that the operator intends to offer a “commercially available mobile device by end of year,” but did not specify whether it would be a smartphone or tablet.

Ray speculated it would likely be the latter. While the T-Mobile CTO didn’t share his reasoning, Samsung Electronics already announced plans to provide 5G tablets for the 2018 Winter Olympics in South Korea.

Meanwhile T-Mobile CEO John Legere was his usual assertive self, talking up his company’s pan-US plans.

AT&T declined to share what spectrum bands it will use for the 5G launch, but confirmed to MWL the deployments will be 3GPP standards-based. AT&T tested 5G at both 28GHz and 39GHz, delivering DirecTV service to customers over the latter in fixed-wireless tests with Nokia conducted in February 2017. T-Mobile’s Ray speculated AT&T’s network would use mmWave spectrum and highlighted the 39GHz band as the “prime candidate”.

However, AT&T is still awaiting regulatory approval for an acquisition of FiberTower, which would give the operator access to a trove of 24GHz and 39GHz licences. The deal was announced quietly in February 2017.