The sale of Apple’s iPhone and iPad in the US is under threat after the US International Trade Commission initiated a formal investigation into the company for allegedly infringing a patent covering multi-touch technology.

The ITC, which has the power to ban the import and sale of products, said it was responding to a request from the Taiwanese touchscreen maker Elan Microelectronics, which has a patent for technology that detects the simultaneous presence of two or more fingers on a touchscreen or touchpad.

This multi-touch technology is at the heart of many Apple products, including the new iPad, the iPhone and iPod Touch, which generate billions of dollars in sales.

Elan, which successfully settled a similar lawsuit against touchpad technology company Synaptics in 2008, accuses Apple of “knowingly and deliberately” infringing the patent. The semiconductor design company is also suing Apple in California, alleging that Apple is infringing two of its multi-touch patents.

An eventual victory by Elan could lead to an exclusion order barring the US import of infringing Apple products. A cease and desist order could also be granted to prevent Apple from selling any of the products that have already been imported.

Analysts said it is likely that Elan is seeking a licensing agreement with Apple for the multi-touch technology.

Touchscreens for mobile devices have become the de facto standard for smartphones, following the hugely successful launch of the iPhone in 2007. The worldwide market for touchscreen mobile devices will surpass 362.7 million units in 2010, a 97 per cent increase from 2009 sales, according to research firm Gartner.

By 2013, Gartner expects touchscreen mobile devices to account for 58 per cent of all mobile device sales worldwide and more than 80 per cent in developed markets such as North America and Western Europe.

“Touchscreens are no longer the preserve of high-end devices and are now being included in many midrange phones as more companies have been driving the consumer market for affordable touchscreen phones,” said Roberta Cozza, an analyst at Gartner. “As phone capabilities increase, consumers are becoming much more aware of the benefits of touch interfaces, and vendors are responding.”

The importance of smartphone technology has led to a blizzard of suits and countersuits, with Apple at the centre.

Apple sued the Taiwanese handset maker HTC last month over touchscreen technology in the US district court in Delaware and asked the ITC to investigate whether the firm infringes its patents. The case is seen as an indirect attack against Google’s Android software, which runs on many HTC handsets. The ITC has yet to respond.

“We think competition is healthy, but competitors should create their own original technology, not steal ours,” said Steve Jobs, Apple chief executive. The Taiwanese firm said it was confident it could defend itself.

Eastman Kodak filed a complaint with the ITC in January, claiming Apple’s iPhone and Research in Motion’s BlackBerry camera phones infringe the photographic company’s patents.

Nokia, the world’s top mobile phone maker, has also sued Apple over patents. Apple has countersued.

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