Customers could begin ordering the new iPhones on Saturday morning and the devices will ship on Sept. 25.
"Customer response to iPhone 6s and iPhone 6s Plus has been extremely positive and pre-orders this weekend were very strong around the world," Trudy Mueller, Apple spokeswoman, said in a statement. "We are on pace to beat last year's 10 million unit first-weekend record when the new iPhones go on sale September 25."
Last September, Apple announced that sales of the iPhone 6 and iPhone 6 Plus reached more than 10 million three days after the launch on Sept. 19, 2014.
"As many customers noticed, the online demand for iPhone 6s Plus has been exceptionally strong and exceeded our own forecasts for the preorder period," Mueller said. "We are working to catch up as quickly as we can, and we will have iPhone 6s Plus as well as iPhone 6s units available at Apple retail stores when they open next Friday.”