Google has defended HTC, which manufacturers the search engine's Nexus One, after Apple accused HTC of infringing 20 of its patents.

"We are not a party to this lawsuit. However, we stand behind our Android operating system and the partners who have helped us to develop it," Google said.

Apple said the patents cover the iPhone user interface and the smartphone's underlying architecture and hardware.

"We can sit by and watch competitors steal our patented inventions or we can do something about it," Apple CEO Steve Jobs said in a statement regarding the lawsuit.

The Google Nexus One is one of the handsets affects by Apple's lawsuit against HTC

"We think competition is healthy, but competitors should create their own original technology, not steal ours."

While Apple did not name Google in the lawsuit, it did name HTC handsets that run Google's Android mobile OS, including the Nexus One, the TouchPro, Touch Diamond and Touch Pro 2, along with those that feature the Windows Mobile platform.

Apple named this group the 'Accused HTC Android Products', and said the collection relied on its technology.

Apple told the US International Trade Organisation (ITC) that as many as 10 of the patent violations involve the Nexus One.

Barry Cohen, a patent and intellectual property attorney at Thorp Reed & Armstrong LLP, speculated whether Apple's lawsuit has a bigger purpose, namely to hit Google.

"Do they have a plan to subsequently [sue] Google? Possibly," he told PC Advisor's sister magazine Computerworld US.

Cohen said that if Tuesday's filings were only a the first step toward taking on Google directly, he expected that Apple had set its strategy and was following a game plan.

"Apple is a smart company," he said.

However, Cohen said it was unknown whether Google has an agreement with HTC that would ensure the search-engine helped defend the mobile phone manufacturer against any patent infringement claims that relate to the Android operating system.

"We don't know what, if any, agreements are in place," he said.

"If HTC hires a law firm that's known for working with Google, that would be a hint."

See also: HTC defends itself in Apple lawsuit