With AT&T just one week away from losing its exclusive hold on the Apple iPhone, the carrier on Thursday pledged to be aggressive in building up its Android offerings, though it said it still has confidence that the iPhone will remain a strong performer.

It's "no secret" that the iPhone would be made available on other U.S. carriers this year, Randall Stephenson, AT&T's chairman and chief executive officer, said during an earnings call with analysts. But "iPhone sales continue to be very strong in the fourth quarter, [which] gives us some confidence in terms of customer loyalty to the network," he said.

AT&T activated 4.1 million new iPhones during the fourth quarter, down from 5.2 million iPhone activations the previous quarter.

Stephenson acknowledged that things might be "rocky" and "kind of volatile" for AT&T when Verizon starts selling the iPhone, but said things will likely stabilize after that initial launch.

AT&T has focused much of its smartphone energy on the iPhone since its 2007 launch, while Verizon has built up its Android portfolio. Now, it appears the two carriers might swap focuses.

AT&T has "not been very aggressive" in adding Android devices to its lineup, Stephenson said. Going forward, however, the carrier is "going to be a heavy participant in the Android market this year."

Stephenson pointed to the Motorola Atrix as one promising Android device AT&T will be offering this year. But Android offerings will be "very broad-based," he said.

AT&T will also add new Windows Phone 7 and RIM products, he said. "We think we're actually going to have a nice mix shift and do quite well in those areas."

Perhaps in a bid to hold on to existing iPhone customers, AT&T talked up recent network improvements. In the last 45 days, AT&T "brought online a significant amount of new capacity," Stephenson said. That boost improved call quality up to 20 basis points, he said.

Stephenson promised greater improvements in New York and San Francisco, where iPhone customers have long complained about spotty coverage and dropped calls. "You should expect voice quality improvement this year," in those areas and elsewhere, Stephenson said.

AT&T also pointed to tablets as an area for growth in 2011. The carrier activated 442,000 iPads and Android-based tablets in the fourth quarter; Verizon activated 86,000 tablets.

"We're really early on in tablets and we think this has a lot of room to run," Stephenson said. "By in large, the tablet market is being dominated by the Apple products, [but] the new stuff is just now coming online, so you're going to see a lot of Android-type tablets come online."

"Tablets are going to be a significant driver to revenue growth," he said.