3G iPhone up for grabs online--or is it?

Update: Overwhelmed by consumer response, O2 has reportedly stopped taking preorders. See this story for more information.

The 3G iPhone has been made available for preorder online from the O2 and Carphone Warehouse Web sites.

The smartphone device is not due to ship until July 11, but beginning today, one-device-per-customer preorders can be placed on the Web sites for delivery on that date.

O2 said preordering was available from 8:00 a.m. British Summer Time on Monday (2 a.m. PDT), while Carphone Warehouse had a preorder page up at 11:00 a.m. (5 a.m. PDT). Both sites, however, have reported problems, which include prospective customers being incorrectly informed that 3G iPhones are out of stock, and the sites running slower than usual.

A Carphone Warehouse spokeswoman said there had been "an issue" with its Web site wrongly stating all 3G iPhone models are out of stock. The retailer is not in fact out of stock of any of the 3G models, she said. Carphone Warehouse's Web site saw a 46 percent increase in traffic after the preorder was made available, she added.

Meanwhile, O2's site currently reports the operator is out of stock of iPhones, yet an O2 spokeswoman said she believes the 8GB version is still available. "The Web site is up and running. But it's a bit slow," she added.

A statement for prospective customers on O2's Web site reads: "Orders will be processed on a first come, first served basis. Your order may be delayed if we have stock shortages or if your order requires further security validation. Certain remote postcodes will require an additional day for delivery."

The spokeswoman said O2 had "roughly split its stock in half"--between its online stores and retail stores. There has been "unprecedented demand" for the 3G iPhone, she added.

Natasha Lomas of Silicon.com reported from London.