Google CEO and Executive Chairman Eric Schmidt has said in an interview with the Wall Street Journal that he thinks it is "extremely curious" that Apple has chosen to sue Google's partners and not Google itself, for patent infringement as the businesses compete in the smartphone market.

"Apple and Google are well aware of the legal strategies of each other," said Schmidt, when asked whether the companies are likely to reach a patent settlement.

"Part of the conversations that are going on all the time is to talk about them."

Apple and Google used to be close partners and right up until 2009, Schmidt sat on Apple's board of directors.

At the time Google's software, such as its search and its Google Maps, featured prominently on Apple's iPhone and iPad devices, with Apple still leading the industry in the field of smartphones and tablets.

However, the two were destined to clash when in 2008 Google launched Android as a free Linux-based operating system to manufacturers of rival handsets to compete with Apple.

Since then, Apple has distanced itself from Google, removing its search from much of its phones' interface and dropping Google Maps from the latest version of its iOS (iOS 6). The company also began suing manufacturers which use Android on their devices, such as Samsung, HTC and LG, for patent infringement - arguing that their devices are rip-offs of its iPhone and iPad.

When Google bought Motorola Mobility last year for $12.5 billion, another smartphone maker in intense patent litigation with Apple, the two companies became directly involved in litigation.

"Obviously, we would have preferred [Apple] to use our maps," said Schmidt. "They threw YouTube off the home screen [of iPhones and iPads]. I'm not quite sure why they did that."

Schmidt said that despite the competition, media reports of the rivalry are overblown, and that the two technology firms are still able to conduct trade with each other.

But he added that the patent litigation between Android-makers and Apple will continue for a while.

"Google is doing fine. Apple is doing fine. Let me tell you the loser here," said Schmidt. "There's a young [Android co-founder] Andy Rubin trying to form a new version of Danger [the smartphone company Rubin co-founded before Android]. How is he or she going to be able to get the patent coverage necessary to offer version one of their product? That's the real consequence of this."

HTC and Apple recently signed a 10-year patent licensing deal which ends all patent disputes between the companies over HTC's Android phone. However, the much bigger legal battles between Samsung and Apple, and Motorola and Apple, continue.