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O2 customers may have to wait until the end of August to get their hands on Apple's new iPhone, even though the device goes on sale tomorrow.

O2 said today that initial supplies of the new iPhone would be limited for several weeks, and that many customers hoping to get hold of one by the weekend were likely to be disappointed.

There would only be "a few dozen" iPhones per store, O2 said, and sales would be limited to one iPhone per customer, two for business customers.

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Based on an average of 40 iPhones at each of O2's 450 stores, that would mean an initial supply of 18,000 devices from Apple. Earlier this week, O2 said that more than 200,000 people had registered their interest in a new iPhone online.

When the operator began taking pre-orders on Monday, its website crashed within an hour. "We are experiencing unprecedented demand for the device, and whilst we are confident that all customers who want iPhone 3G will get one by the end of the summer, initial supply is limited and will be for some weeks," O2 said today.

O2 said it had stopped taking pre-orders online, as supplies had run out. A spokesman added that the company was "working closely with Apple" to get more 3G iPhones. An Apple spokesperson declined to comment.

Carphone Warehouse, the only other distributor of the device apart from Apple, said its initial online stock sold out within a few hours yesterday, but declined to give any further details about supply.

Some O2 stores will open at 8am tomorrow, but others not until 9:30am. There are more details on opening times on O2's website. Customers wanting to buy the device in store are advised to bring two forms of ID, a valid credit card, and proof of address.

Initially, the new iPhone will only be available to old iPhone customers wanting to upgrade, or new customers signing up afresh. O2 customers on contracts with other devices are obliged to serve out those contracts before upgrading.

Times Online rang several O2 stores in London, Birmingham and Manchester this morning. None knew how many 3G iPhones they would have tomorrow, saying they would only find out when the delivery arrived later this evening.

The 3G iPhone, a combined phone, e-mail, music and video player, and internet device, is an upgrade to the earlier model that was released in the UK in November. Sales of the old iPhone, which initially cost £269, have been disappointing, but the new device - which will be free on contracts of £45 a month or more - is expected to be more popular.

When Steve Jobs, Apple's chief executive, unveiled the new iPhone last month, he admitted that many customers had been turned off by the high price tag.

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