Component shortages are holding back supplies of the HTC Evo, hampering Sprint's efforts to attract users to its 4G network.
On its site, it says simply "Sold out. Check back later - more are on their way".
The reason is that the phones' touchscreens, supplied by Samsung, are in short supply. While Samsung is working on increasing capacity, its new facility won't come online until 2012. In the meantime, Verizon and AT&T are planning to launch rival high-speed networks, probably by the end of the year.
Sprint chief executive Dan Hesse told the Wall Street Journal that the shortages were hindering the takeup of 4G. "We thought we would have more of a head start than we'll end up having," he said.
It's the same problem Verizon's had with the Droid Incredible range - indeed, the company website says it'll have no new stock for another four weeks.
A spokesman for HTC told the WSJ that the company was checking flights to the US to see if it could get some last-minute cargo space, aiming to supply new stock to both Sprint and Verizon.
It's also trying to drum up more suppliers, recently signing a deal with Sony.