Portable media player maker Creative Technology has said that US authorities will look at whether Apple's rival iPod player infringes one of its patents.
Apple has three-quarters of the global digital music player market
The firms have swapped patent lawsuits in recent months, but Creative said the US International Trade Commission (ITC) was now launching a probe.
Creative has asked the ITC to issue an order stopping Apple from marketing, selling or importing iPods into the US.
It claims the iPod infringes its patent for a music player navigation menu.
On Wednesday, Creative filed a complaint alleging that iPods infringe on its patent for software it uses to organise and access music on its Nomad and Zen-branded media players.
It said the ITC will refer the case to a judge who will hold hearings before making an initial determination as to whether an infringement has taken place.
The ITC normally issues a ruling 12 to 15 months after an investigation begins, Creative said.
Creative was one of the first companies to sell digital music players back in 2000, but it has struggled against the market dominance of the iPod since it was launched in 2001.
It plunged into the red earlier this year, blaming its $114m (£62m) losses for the three months to March on the plunge in MP3 player prices and its need to get rid of stock.
But it pledged to return to profit in the second half of 2006, saying it was renewing its focus on high-margin products, such as computer sound cards.