About 19 million US mobile phone users are ready to pay as much as $599 (£300) for Apple's iPhone, nearly double the number Apple has projected it will sell by the end of 2008, according to an M:Metrics survey.

M:Metrics’ May poll also showed that AT&T made a smart move when it made an exclusive deal with Apple to be the iPhone's sole American carrier, said analyst Mark Donovan. "Two-thirds of the people who said they have a strong interest [in buying an iPhone] currently subscribe to AT&T's three biggest competitors," said Donovan. "In this mature market, it's all about stealing customers from competitors."

However, research firm Gartner has previously suggested that an exclusive deal with operators might not work in Europe, suggesting the fragmented nature of the European mobile phone market might cause problems for the iPhone. (See also '7m Brits can't wait for iPhone'.)

Yet, demand for the iPhone in the US will be massive at the start, according to Donovan. Of the more than 11,000 American mobile phone users surveyed, 9 percent, or roughly the equivalent of over 19 million of all US subscribers, said their purchase intent was high. Apple CEO Steve Jobs has forecast sales of 10 million iPhones in the first 18 months.

M:Metrics made a point of reminding those it polled that the iPhone would debut at $499 or $599, and that they would have to sign an AT&T two-year contract. Still, that didn't seem to put off potential buyers.

"I don't think we've ever seen a mobile phone that's generated this much awareness," said Donovan. That will probably translate into a big opening weekend, he added, making the analogy to a Hollywood blockbuster opening. "Apple's picked Friday as the first day of sales, just like a new movie."

After that weekend, however, the true test begins. "When we shift from everyone intoxicated with the iPhone, and people start purchasing it and showing it off, the question mark will be, is it able to maintain the interest?" said Donovan.

Even the unknowns - such as the price of the AT&T plans - won't dent the iPhone's opening, Donovan said. "The people who are going to line up that first weekend, they've jumped over those hurdles already," he said. But once that group gets its iPhones, contract pricing may be a barrier to some buyers.

Other problems might surface, too. "Will there be a 'gotcha,' like the easily-scratched screen on the first [iPod] nano?" Donovan asked.

Of AT&T's major competitors, T-Mobile USA is the one that will lose the most customers to the iPhone. "There's stronger interest in it from T-Mobile users than from Verizon or Sprint," Donovan said. "That's actually a credit to T-Mobile, because it's gone after pretty youthful customers who have adopted advanced devices like the Sidekick."

M:Metrics' survey said 12.5 percent of T-Mobile subscribers expressed a high interest in buying the iPhone, compared to 8.1 percent for Sprint Nextel and 6.7 percent for Verizon Wireless.