SAN FRANCISCO--On the eve of the Apple iPhone's sale, the top executives of Apple and AT&T defended their decision to rely upon AT&T's slow EDGE wireless data network, rather than a faster network that is less widely available.

Early reviews of the iPhone, while positive, have faulted the slower network because it will limit the palm-size wireless computer's greatest strength--making the Internet easily accessible on the go.

"It doesn't concern me," said Randall L. Stephenson, the new AT&T chief executive, in a joint telephone interview on Thursday along with Steven P. Jobs, Apple's chief executive. The fact that the iPhone offers faster Wi-Fi networking would more than make up for the relatively slow 300-kilobit-a-second pace of its cellular data network, he suggested.

The phone goes on sale Friday at 6 p.m. at Apple and AT&T stores.

Both executives said they were not certain what to expect at the stores on Friday evening. Lines have begun to form in some parts of the country, but there is uncertainty whether a $500-to-$600 consumer product can attract millions, rather than tens of thousands, of early customers.

"We've certainly built a lot of iPhones, although it may not be enough," Jobs said. Changing a forecast in the consumer electronics industry is difficult, he said, because of the long lead times necessary to build components like semiconductors.

And Stephenson said, "I think it's going to be an exciting evening." He said his company had added about 2,000 employees in an effort to handle what it expects will be large crowds.

Jobs said Apple planned to limit sales to two for each customer, and Stephenson said AT&T would restrict purchases to a single phone.

Concern surrounding the AT&T network could be one of the biggest unknowns as the product rolls out. That did not diminish Stephenson's enthusiasm.

"I got to tell you, carrying this thing around and experiencing those kinds of speeds on a wireless handset, your imagination begins to run in terms of what's possible," he said, "and by the way, there's not a 3G network available in Ottumwa, Iowa," referring to the so-called third generation of Web-enabled cell phones that require faster networks. "If you want to sell these devices in a variety of places, EDGE (Enhanced Data rates for GSM Evolution) is the only opportunity you have."

The thinking behind the trade-off
AT&T has invested $16 billion in its network over the last two years, and the network is now designed to handle the expected increase in wireless data users, he said, adding: "Capacity won't be an issue. The network is ready."

Jobs said the decision to hold off on using AT&T's faster HSDPA network--shorthand for High-Speed Downlink Packet Access--was a trade-off.

"EDGE is good, but you'd like it to be faster," he said, suggesting that the availability of local Wi-Fi networks would make up for the EDGE network's slower speed.

Jobs also said Apple's hardware design team had decided against using the more advanced 3G chip sets because they were relatively power-hungry. As a result, Apple improved the battery life of the iPhone.

"We felt it wasn't the right trade-off now," he said. "I'm sure that will all change in