The 30-gigabyte Zune, which stores up to 7,500 songs, 25,000 pictures or 100 hours of video, was introduced in the US yesterday. It sports a wireless feature that allows users to import their iTunes music collection and “beam” songs to each other.

After several years in development, the Zune is Microsoft’s attempt to topple the iPod from its position as the world’s best-selling MP3 player. The Zune even has its own download music store, aping Apple’s success with iTunes.

The Zune has hit American stores with a $250 (£130) price-tag. But Microsoft is seeking to keep its launch low-key, and has given no dates for a worldwide release.

That has not stopped so-called early adopters seeking out imported models. Zunes are already being offered on eBay for £230, even though British users will not have access to the Zune Marketplace online store.

Gordon Frazer, managing director of Microsoft UK, said: “We’re going to see how this goes in the US and what lessons we learn and then make the right decision for the UK.”

Microsoft is expected to have the Zune in Britain for Christmas 2007, but will come under pressure to bring the date forward. Computer games fans are already paying £1,200 on eBay for the Sony PlaySation 3 console, only days after its release in Japan.

Gadget experts said that the ability to connect Zunes with each other wirelessly was a key weapon in its battle with the iPod. “They’ve got a single differentiating feature — sharing,” said Michael McGuire, of Gartner Research.

One drawback is that shared songs are erased from borrowers’ Zunes after three days or after being played three times, even if only snippets are listened to. Songs are bought permanently through the Zune Marketplace, which will have two million tracks.

While the sleek iPod has become a design classic, there was disappointment with the bulkier Zune, which has a three-inch (7.5cm) screen and comes in black, white or brown. Mr McGuire said: “It doesn’t break any ground style-wise. I would have expected them to leapfrog Apple.”

Record companies are keen to back a challenger to Apple’s dominance of the music download market and have preloaded the Zune with hits.

Microsoft has courted musicians and record companies aggressively, even promising Universal Music a portion of Zune player sales revenues. Meanwhile, sales of the Apple player have fallen quarter-on-quarter this year for the first time, while opinion polls have suggested that young technophiles no longer idolise the iPod as they did once.

Apple, which enjoys 80 per cent of the market, has redesigned its Nano, the world’s most popular music player, in anticipation of the challenge.

Chris Stephenson, marketing manager for Zune, said: “We’re delivering not only a device, but a shared, social experience that will be shaped by the collective imagination of consumers.”

But Steve Jobs, chief executive of Apple, said: “I’ve seen the demonstrations about how you can find another person using a Zune and give them a song they can play three times. It takes for ever. By the time you’ve gone through all that, the girl’s got up and left.”

Michael Brooks, editor of T3, the gadget magazine, said: “[Microsoft] have certainly got the money to go after Apple. It depends if they have the product savvy — and they need to get the design right. They have got a mountain to climb.”

• Six airlines will allow iPods to be connected to in-flight entertainment systems next year. Apple said Air France, Continental, Delta, Emirates, KLM and United will offer seat connections to power iPods and allow video from them to be watched on seat-back screens.

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