Sprint Nextel CEO Dan Hesse says shortages of its first 4G phone, the HTC Evo, are cutting into potential sales as rival companies prep their own fourth-generation networks, according to an interview reported by The Wall Street Journal.

Sprint said the number of Evo handsets sold on launch day in early June was in line with the number of Samsung Instinct and Palm Pre devices sold over their first three days on the market combined, leading to what the carrier called “temporary shortages.”

The HTC Evo is currently out of stock and doesn’t have a ship date, according to Sprint’s website. The carrier recently announced it would be carrying another 4G-capable phone, the Samsung Epic, but the device appears to be some ways off as Sprint said pricing and availability would be announced “in the coming months.”

The Samsung Epic has an Active Matrix Organic Light Emitting Diode (AMOLED) touchscreen, a type favored by makers of Android devices. Last week, iSuppli warned that short supplies of AMOLED displays were a threat to Android manufacturers. The Evo features an LCD screen.

The shortages come as Sprint’s competitors are moving ahead with their 4G plans. Sprint has pitched its head start in 4G as a major competitive advantage, but that edge could diminish as Sprint’s competitors move aggressively with their own 4G deployments.

Verizon Wireless plans to launch its LTE network in 30 markets sometime this year, with an aggressive deployment plan for nationwide 4G coverage by 2013. Verizon is currently conducting trials of the technology and has not announced specific launch dates for the network.

T-Mobile USA claims its HSPA+ network, which will cover up to 185 million people by the end of the year, already delivers 4G speeds. AT&T plans to begin commercial deployments of its LTE network in 2011.

“We thought we would have more of a head start than we’ll end up having,” Hesse told The Wall Street Journal.