NEW YORK - A delayed top-of-the-line BlackBerry phone from Research in Motion Ltd. is still undergoing testing by AT&T Inc., and RIM's co-CEO implied that the carrier wants to avoid the chorus of complaints about performance that greeted the new iPhone this summer.

AT&T and RIM said in May that the BlackBerry Bold 9000 would go on sale in the U.S. this summer, but it's not available, and no date has been announced. It is on sale in some foreign markets.

RIM co-CEO Mike Lazaridis said Thursday that the phone is still undergoing the certification process in which AT&T tests all new handsets to make sure they work well on its wireless network.

"There's great scrutiny, as you might know, on that network and a certain device. So I guess everyone wants to be sure on every last test," Lazaridis told The Associated Press.

Apple Inc.'s iPhone 3G went on sale in July, with AT&T as the sole U.S. carrier. Customers soon started complaining of slow data downloads and dropped calls on some units. AT&T and Apple have not directly acknowledged a problem, but Apple has released a software update that was supposed to improve performance. The majority of iPhones appear to be working well.

Lazaridis appeared confident that the Bold would not be subject to the iPhone's problems.

"We're very meticulous about what our product does," he said.

AT&T spokesman Mark Siegel would not confirm that the Bold was still in testing and said only that it would come out this year.

The delay of the Bold has weighed on RIM's stock. Because of the postponement, the company now will be launching several new phones at once in the coming months. Waterloo, Ontario-based RIM said last week that expenses from those rollouts would eat into short-term profits.

RIM's U.S. shares fell $1.04, 1.7 percent, to close at $60.96 on Friday.