HTC has a string of hits on its hands when it comes to Android-based smartphones. The Droid Incredible, which was introduced back in early June, is still hard to come by due to component shortages and Verizon's website says that new stock won't come in until August 9.

It now appears that another HTC phone is being held back by component shortages: the Sprint's EVO 4G. According to the Wall Street Journal, the main holdup in EVO 4G production comes from the Samsung touchscreens that are used on the smartphone. To make matters worse, Samsung won't have additional production capacity for touchscreens until its new factory is completed in 2012.

Whereas Verizon has a date set in stone for when it will receive additional stock of Droid Incredible smartphones, Sprint simply states on its site:

Sorry, this device is so hot we can’t keep it on our virtual shelves. Check back later – more are on their way!

The EVO 4G is the first smartphone available to U.S. customers with 4G connectivity. Sprint is also currently the only major wireless provider in the United States to offer limited 4G connectivity (courtesy of WiMAX), but larger rivals Verizon and AT&T are quickly moving to ready their competing networks.

"We thought we would have more of a head start than we'll end up having," said Sprint CEO Dan Hesse.

Verizon has begun user trials of its LTE 4G service in five cities and is expected to have the service available in 25 to 30 markets by the end of the year covering 100 million people.

AT&T is reading its LTE network for a late 2010/early 2011 launch.