Apple was counting the cost today of choosing a slower network on which to run its new iPhone in the US after new owners reported being unable to access the internet on the device for most of yesterday.

Across the breadth of the country - from Hawaii to Illinois - there were reports that AT&T network was down, apparently as a result of intense use of the phone by the more than 500,000 people who are reported to have bought it since it went on sale Friday.

A spokesman for AT&T said that the problems experienced on its EDGE network, which carries all "data", such as internet pages, requested by iPhone users, were not connected with the new phone, and by evening the situation was beginning to right itself, but not before websites had been deluged with complaints by owners unable to use their new toy.

"It was near impossible to connect either to get my e-mail or access a website," Phil, a user in San Diego, wrote on the Engadget website. "I tried my AT&T BlackBerry (8800), which uses the same network and it worked fine."

Another, based in San Fransisco, wrote: "There seems to be no real explanation as to why the US carriers suck so bad — they are some of the most profitable operators in the world, yet they just don't seem to be able to build out their networks enough so that there's ubiquitous coverage."

Difficulties were also experienced by users in Texas, Colorado and the state of Washington.

Apple's decision to have the iPhone run on EDGE, which is slower than 3G networks but has better geographic coverage in the US, was described by a reviewer in The Wall Street Journal as a "major drawback" of the device.

Some users also reported having difficulty activating their phones over the weekend, a problem that AT&T attributed to initial overload which had now, the network said, been rectified.

"There is a small percentage of iPhone customers who have had a less than perfect activation experience,” an Apple spokeswoman said.

Alan Brown, an analyst specialising in wireless technology at Gartner, said: "It's a bit like New Year's Day phone calls. A network will make certain provisions to cope with high volumes, and once that's exceeded, it's likely the network will fall over."

Mr Brown said that the uptake of the iPhone would have "stretched" AT&T more than any other new handset — partly as a result of the unlimited internet usage that comes with all iPhone price plans, but that it was possible there were other sources of the outage than the wireless or "air" network, such as servers or other telecommunications equipment.

If, as has been widely predicted, Apple brings out a 3G version of the iPhone in Europe, it was likely that the networks would be better equipped to cope with high data volumes, Mr Brown said, although there would still be concern about "buckling", particularly because of the bullish forecasts about early sales.

Faster download speeds could be guaranteed by including a higher-end 3G chipset in the phone, but that would depend on whether Apple was willing to increase the cost of the handset by as much as 50 per cent, he said.

In a separate development, it emerged today that at least one British company had secured contracts to supply parts to the iPhone.

Wolfson Microelectronics, an Edinburgh-based firm, is supplying Apple with a sound component known as an audio codec.

ARM Holdings, based in Cambridge, is reported to have licensed some of its microprocessor designs to other iPhone suppliers, such as Samsung, but the company declined to confirm this.