Apple Inc. sold more than a million units of its latest iPhone model in the first three days, making it the most successful debut for a smart phone yet.

The iPhone 3G S went on sale Friday in the U.S. and seven other countries.

When Apple Inc. launched the previous model last year, it also sold one million units in the first three days, but that model launched simultaneously in 22 countries.

Piper Jaffray analyst Gene Munster had expected the Cupertino, Calif., company to sell half a million 3G S in the first three days.

"Customers are voting and the iPhone is winning," said Steve Jobs, Apple's CEO. It was the first time he was quoted in a company statement since he went on leave for unspecified medical reasons in January. The company has said that Jobs, who has battled pancreatic cancer, is returning to work at the end of the month.

The Wall Street Journal reported Saturday that Jobs had a liver transplant two months ago in Tennessee and that he will likely work part-time, at least initially. Apple has not commented on the report.

The launch of the iPhone 3G last year turned messy, as Apple and phone company servers failed to cope with the load of new customers trying to activate their phones. That problem recurred Friday with the launch of the 3G S, but to a smaller extent. Some customers who tried to activate the phone at home got messages that the process could take 48 hours to complete.

Some customers got e-mails on Sunday promising a $30 credit at Apple's iTunes store as compensation for the hassle.

Apple did not break down where the million units were sold. Dallas-based AT&T Inc. is the iPhone's exclusive carrier in the United States and has said it sold hundreds of thousands of phones via pre-order.

The sales figures demonstrate that the iPhone's cachet is intact, and even growing, despite reinvigorated competition. Other manufacturers are putting out phones that mimic some of the iPhone's signature features. In particular, the newly released Palm Inc.'s Pre, available exclusively for now through Sprint Nextel Corp., has generated a lot of buzz and favorable reviews.

The iPhone 3G S has a faster processor and a better camera than the 3G, among other differences. The 3G is still on sale, for $99. The 3G S costs $199 or $299 depending on the memory capacity.

Apple shares fell $2.48, or 1.8 percent, to $137 in afternoon trading Monday.