AT&T has been promoting 4G speeds for quite some time, but the second biggest wireless carrier in America is finally making it official with upcoming launch of its LTE network.

At the Bank of America Merrill Lynch Media, Entertainment & Communications conference this week, AT&T chief financial officer John Stephens said AT&T will launch its LTE network in Atlanta, Chicago, Dallas, Houston and San Antonio next week on Sept. 18. By year's end, Stephens says there will be 75 markets nationwide with AT&T LTE networks.

Prior to this launch, AT&T had been promoting 4G speeds even without the LTE network in place. The company used its HSPA+ network for this promotion, saying it had faster network speed than the typical 3G network. While this may be true, the International Telecommunication Union basically dismissed the idea that AT&T's HSPA+ network was a 4G network.

Verizon, AT&T's biggest rival, has already launched a 4G LTE network with several products, including the recently released Motorola Droid Bionic. In terms of networks, Verizon has LTE coverage in 117 cities across the U.S. Sprint and T-Mobile also offer legitimate 4G networks as well, although many analysts are not as sold on Sprint's WiMAX 4G network and its long-term ability to compete against LTE.

BTIG Research analyst Walter Piecyk did a speed test earlier this year and said Verizon's LTE blew away Sprint's WiMAX in 1,000 speed tests. Verizon's LTE network delivers downlink speeds of 5-12 Mbps and uplink speeds of 2-5 Mbps. Sprint's WiMAX average about 1 Mbps both down and uplink speeds.

In anticipation of its 4G LTE launch, AT&T has already promoted and begun to sell two LTE capable phones: the USB Connect Momentum 4G modem and the Mobile Hotspot Elevate 4G. These phones were both made by Sierra Wireless. The phones cost $49.99 and $69.99 respectively and come with two year contracts. There's also an LTE tablet, the $700 HTC Jetstream.

Stephens also said he is confident AT&T's proposed acquisition of T-Mobile for $39 billion will go through despite the hurdles it faces from the U.S. Department of Justice. The DOJ recently filed a lawsuit against AT&T for the acquisition citing antitrust concerns. He says the company is open to settling with the Department of Justice.

Follow Gabriel Perna on Twitter at @GabrielSPerna