By Prince McLean

Published: 07:00 PM EST

After selling 5.2 million iPhones in fiscal Q3, including a million units that sold in the first three days, Apple has announced being "unable to make enough 3GSs to meet demand."

Voracious demand for the latest iPhone has helped restrict it to 18 launch countries out of the 80 where Apple currently sells iPhones. With demand for the new iPhone 3GS far outpacing supply, Apple COO Tim Cook admitted today that limited stock could briefly delay the planned launch of the new iPhone in more countries overseas. Cook said Apple expects to have the iPhone 3GS available in most nations where the iPhone 3G is currently available by the end of the September quarter.

Cook said channel iPhone inventory was flat sequentially in comparison with the last quarter and that the "channel is not loaded." He admitted that with demand for the iPhone 3GS currently very high, it's possible that some overseas launches could be delayed. "In terms of affecting the country rollout, I believe the vast majority of the countries that we are selling the 3G in we will be selling the 3GS I think by the end of the fiscal quarter," he said. "It may move a date by a few weeks here or there."

The company also hopes to continue to expand its reach. "The world has more than 80 countries," Cook said. During a question and answer session, Cook was asked about Apple's plans to enter China with the iPhone. "Nothing to add today specifically," Cook answered, "other than it continues to be a priority project and we hope to be there within a year."

Cook also said wireless carriers worldwide are thrilled by the lower churn rate the iPhone delivers, helping them to retain loyal customers. Asked about other products Apple might tie to providers' wireless contracts, such as notebook and netbook sales, Cook said the company was currently focused on working with carriers on the iPhone and had nothing else to announce.

Speaking of AT&T specifically, Cook said Apple has an excellent relationship with the mobile provider and is very happy with it. When asked about phone sales being constrained by AT&T's network capacity, Cook deferred the question to AT&T itself, but noted that providers were making more investments in their networks to meet consumer demand.

Cook also said that Apple had initially studied the wireless market and determined that "what we could do really well is build hardware" with features that were "revolutionary," leaving the service side to companies with more skills in networks. "that's their business and they're quite good at it," Cook said.

Asked if the $99 iPhone 3G was a major contributor to new sales or more of a loss leader to bring customers to the new iPhone 3GS, Cook said it was still early to tell how popular the new lower priced model would be, as many of the early waves of buyers were upgrades who were more likely to pick the new phone.

Cook also called iPhone 3.0 the "world's most advanced mobile platform" and noted the 65,000 library of iPhone apps had reached a 1.5 billion milestone of downloads, drawing comparisons with the one to two thousand apps available for RIM Blackberry and Nokia phones, or the 5,000 apps advertised for the Android platform.