iPhone 6S

Apple on Wednesday debuted its newest smartphones, the iPhone 6S and iPhone 6S Plus, giving the devices a new pressure-sensitive display, zippier processor and more powerful camera.

"What we have to show you today is really awesome," CEO Tim Cook said onstage at Apple's presentation, held at the Bill Graham Auditorium in downtown San Francisco. "While they may look familiar, we have changed everything about these new iPhones."

This year's iPhone is Apple's off "S" year. That means Apple keeps the basic design of the device the same but adds other features to attract buyers, like the Siri digital voice assistant in the iPhone 4S and the TouchID fingerprint reader in the iPhone 5S.

A marquee feature for this year's iPhone 6S was expected to be the Force Touch technology used in the Apple Watch, a pressure-sensitive display that responds to various types of touches. The company instead unveiled 3D Touch, a feature that appears to have the same capabilities.

In another bigger change, Siri can be activated via voice for the first time, allowing a user to ask the digital assistant questions or play music by saying "Hey Siri" while washing dishes or preparing a meal. In older models, Siri can only be activated by pressing the phone's home button. The new feature helps Apple catch up to other devices, such as the Amazon Echo speaker and many Android phones, that already offer similar functions.

The new 4.7-inch 6S and 5.5-inch 6S Plus, which are the same size as last year's models, will be available for preorder starting Saturday and available Sept. 25 in the US, UK, China, France, Japan, Australia and other markets. The base-model iPhone 6S will cost $649 off-contract, following Apple's typical pricing model. Prices for the 6 and 6 Plus will be knocked down by $100.

The new phones will include Apple's new A9 chip, which the company claims is 70 percent faster at computing tasks than last year's A8 chip in the iPhone 6 and 6 Plus. "It delivers a big jump in performance," Apple executive Phil Schiller said onstage. "It's going to make using our phone faster and a lot more fun."

The devices also come with a new 12-megapixel iSight back-facing camera, a boost from the 8-megapixel cameras in last year's phones, and are available in four finishes: silver, gold, space gray and a new rose gold finish. Additionally, the new phones will come with faster LTE and Wi-Fi wireless connections, a faster TouchID sensor, the ability to shoot high-resolution 4K videos and the phone's screen now acts as a flash for selfie pictures.