T-Mobile Chief Technology Officer Neville Ray says 5G will be a second-half story for the company.

Eager to jump on T-Mobile's 5G network? You're going to have wait a little longer.

T-Mobile Chief Technology Officer Neville Ray said in an interview that the company won't be formally launching its 5G service in its first 30 cities until the second half of 2019. A year ago, Ray told CNET that the launch would happen in the first half.

Ray said he had hoped at the time that handset manufacturers and chipset makers would be ready to build a phone that taps into the lower-band 600 megahertz spectrum, which it's using to power 5G across a large swath of the country. The first 5G smartphone, Samsung's Galaxy S10 5G, uses high-frequency bands compatible with Verizon, AT&T and Sprint.

Ray's concession throws a wrinkle into the 5G race, as carriers push to the be first to the next-generation wireless technology, which promises a much faster and more responsive network. AT&T has already launched 5G in a dozen markets, but in limited areas, while Verizon has a home 5G network. Sprint, meanwhile, said it plans to launch 5G in four markets in May.

The delay also underscores the complexity of building a 5G network, and the bets companies must make on what kind of spectrum they can use. Verizon and AT&T initially championed millimeter wave spectrum because it can deliver super-high speeds, but with limited range. T-Mobile opted for lower-band spectrum that has slower peak speaks, but better coverage.

Much of the early investment went into devices that use millimeter wave spectrum. While Ray said T-Mobile would sell the Galaxy S10 5G, he was unsure if it would even market the benefits since the company's own millimeter-wave deployment was so limited.

He said he didn't worry about AT&T and Verizon pulling ahead in the 5G race because of the limited range of millimeter wave.

"You can't go to a US consumer and charge them a big premium and it works on three street corners," Ray said.

Ray applauded Sprint for at least staking a claim and saying it would cover more than 1,000 square miles by the first half. He's waiting to hear about AT&T and Verizon's coverage plans.

AT&T and Verizon weren't immediately available for comment.

Ray said the company would go big with 5G in the second half once it gets a device that can tap into its 600 MHz spectrum. He declined to comment on which company would supply the phone.

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