Owing to the soaring demand of Apple's recently launched fifth-generation iPhone - the iPhone 4S, an inventory survey reveals that most Apple stores in the U.S. and abroad have run out of stock on a daily basis.

A recent survey by an analyst of Deutsche Bank revealed that approximately 30 retail outlets are experiencing stock drains of the iPhone 4S on a daily basis. The analyst, Chris Whitmore, said that 85 to 90 percent of the stores run out of inventory every day. A report by Tuaw News suggests that online orders are also backlogged and subject to delay.

Apple employees are directing customers to make an online appointment (first come first serve) for next day pickup at nearby Apple retail stores as stocks appear to be refreshed daily at most locations, said Whitmore in the report.

Most stores are selling their entire stock and are urging the customer to make appointments for next-day pick-ups, in order to avoid any inconvenience.

The iPhone 4S, which was launched on Oct. 4, sold over a million units in the first 24 hours of it being made available on the market.

According to Apple Insider, inventory checks with carriers AT&T, Sprint and Verizon found that supply of the iPhone 4S was more sporadic. Most stores Whitmore contacted indicated that shipments were infrequent, and there was no indication as to when Apple would send more units.

Looking at the towering demand and strong sales, the report forecasts Apple should be able to sell more than 28 million iPhones during the holidays.

Whitmore said the demand continues to track very strongly, and supply is still a gating factor, in both U.S. and international market.

The new phone was first launched in seven countries, immediately followed by 22 more from Oct. 28. Apple, on Friday, started taking pre-orders for the iPhone 4S in fifteen more countries, including Hong Kong.

According to Ticonderoga Securities analyst Brian White, Apple's iPhone 4S demand has shown very positive signs in the growing market of Greater China; Hong Kong represents the first entry of the new smartphone into this area.

Our checks indicate that pre-orders in Hong Kong were sold out within ten minutes after becoming available, said White in a report.