The Apple iPhone's success in the US is not a sure thing, according to a recent survey.

The iPhone has generated a lot of excitement over the last few months and the device hasn't even been released yet. But a survey conducted by market research firms IDC and Market Insight cast doubt on its prospects.

Among the reasons cited for the uncertainty of whether the iPhone will be a runaway success is the price for the service plan through AT&T in the US. To date, Apple and AT&T have declined to provide details on the cost of the service plan for the iPhone.

"Despite all the hype, there is little clarity on Apple's (and AT&T's) service plans for the device. This lack of clarity could adversely impact consumers' purchase decisions," said Shiv Bakhshi, director of mobility research at IDC.

According to the data collected, only 10 percent of respondents were interested in paying full price and signing a two-year contract with AT&T. Nearly 18 percent of the respondents indicated a willingness to buy the iPhone if it were priced under $299 - but the iPhone will retail for $499 and $599.

AT&T is currently the only service provider in the US that will carry the iPhone, which means consumers will have to switch if they want the device. Paying penalties to existing service providers was cited by respondents as another reason for not buying the iPhone when it is released. About 17 percent of the respondents indicated that they would buy an iPhone if it were offered by their current mobile carrier.

"Apple loyalists alone can make the initial launch a 'success.' But beyond that, it will be interesting to see the extent to which the iPhone hype, and the curiosity it has generated, translates into actual purchasing intent," said Bakhshi.

A report released yesterday by mobile market research firm M:Metrics showed strong interest in the iPhone. According to that report, 67 percent of those who were most inclined to purchase an iPhone are subscribers on other carrier networks. People that took the survey were also informed of the iPhone price and the five-year AT&T exclusive.

"Beyond these important adoption issues, a number of questions remain about how consumers expect to use the iPhone," said Chris Hazelton, senior analyst, mobile device technology and trends, at IDC. "The capabilities of the device, and its supporting network, present the next set of potential barriers to widespread adoption. These issues may ultimately determine the success, or failure, of the iPhone."