San Francisco - Pre-release sales of the Google-powered mobile phone offered by T-Mobile are three times as high as the company predicted, the German-owned carrier has revealed.

The so-called G1, which is the first mobile phone to utilize Google's Android operating system, will officially become available on October 22. But existing customers of T-Mobile have been able to pre-order the device, which is manufactured by Taiwanese company HTC, since it was unveiled last month.

T-Mobile declined to specify how many G1s had been ordered by customers. But reports indicate that some customers trying to pre- order a G1 were told there were none left.

The high demand seems to be feeding off the success of Apple's iPhone, which boosted consumer and business interest in smart phones. According to figures released Monday, the iPhone now accounts for 17 per cent of the smart phone market in the US.

According to research firm The NPD Group, 30 per cent of US consumers who bought the iPhone 3G between June and August switched to AT&T, the exclusive operator for the iPhone, from another carrier.

The iPhone 3G was the number-one smart phone based on unit sales from June to August, NPD said. The BlackBerry Curve was number two, followed by the BlackBerry Pearl.

NPD director Ross Rubin said smart phones were beginning to supplant simpler cell phones among US consumers.

"The momentum in the marketplace is definitely moving toward smart phones," said Rubin. "The smart phones are just becoming much more consumer friendly and the form factors are sleeker. Social networking on smart phones is increasing and consumers are more amenable to having access to those capabilities on the go." (dpa)