Verizon Wireless is pushing back the release of the Droid Charge by a few days in the wake of its LTE network outage, which only lasted a day but frustrated many users of the new 4G phones.

The outage started on Tuesday night when users of HTC Thunderbolt phones started reporting that they could not connect to the network. The Thunderbolt is the first 4G-capable phone that Verizon rolled out for its network, introduced with much fanfare at the Consumer Electronics Show in January.

The problems with the LTE network occurred the day before Verizon was to launch the Droid Charge, which was set to go on sale April 28.

Verizon hasn't yet said what caused the network outage.

We have determined cause of 4G LTE issue & are working with major vendors to restore connections. Details as they come, the company announced on its Twitter feed Wednesday.

Verizon spokesman Jeffrey Nelson confirmed that there was a problem, noting that 4G smartphones like the Thunderbolt were still able to make calls. Thunderbolts making voice calls may get 1XRTT data, meaning that the phone gets a voice connection only. Thunderbolt phones can work on the 3G network, but that doesn't offer the speed of data transmission that LTE network does.

Since December, Verizon has turned on its 4G network in 45 metropolitan areas.