Yesterday we told you that the shipping dates for the new iPad had slipped in both the US and UK to March 19th. Those two countries, and a selection of others, had their ordering dates pushed back from March 16th, as the first allotment of iPads for online shipment were snapped up by eager customers.

Now, Apple has confirmed that its pre-order stock of iPads has sold out, reports USA Today.

“Customer response to the new iPad has been off the charts and the quantity available for pre-order has been purchased,” Apple told the publication in a statement. “Customers can continue to order online and receive an estimated delivery date.”

Those dates will doubtless continue to creep outwards as more users order up the new iPad. Apple says that there will definitely be stock to purchase in its retail stores come Friday, but I would expect lines to be long. Apple is also selling the iPad at several retail partners, including Best Buy and Radio Shack, but if you’re looking for an iPad on launch day, your best bet is still Apple.

The company’s stores generally get the largest stock of their launch-day devices and the line can take on something of a carnival atmosphere for Apple enthusiasts. Apple Retail Stores normally open around 8am on launch days as well, so get there early.

So far, the demand for the device is looking to be fairly high, I wouldn’t be surprised to see it set a few records. The first iPad sold 300,000 units on its first day of sales and the iPad 2 sold 500,000 during its first weekend. It will be interesting to see how demand for the new iPad stacks up.

The new iPad is priced at $499 for 16GB, $599 for 32GB, $699 for 64GB. And $629, $729, and $829 for 4G. It will be available on March 16th in the US and is available for pre-order now. It will be available from March 23 for 32 other countries. The iPad 2 will continue to be sold for $399 in a 16GB flavor and $529 for a WiFi + 3G 16GB model.

For more information about Apple’s new iPad, check out our roundup post here.