A San Francisco appeals court has unanimously rejected a petition filed by music-swapping service Napster, in which the controversial music distribution company sought a re-examination of an injunction handed down against it earlier this year.

A triumvirate of US Court of Appeals judges ruled, on 12 February, that Napster infringed record company copyrights through the operation of its music file-trading service. Napster then asked that the entire Appeals court look at the case.

Court documents filed last Friday show that the court denied Napster's request. The court's ruling marks just one part of a lengthy battle between Napster and music labels represented by the RIAA (Recording Industry Association of America).

The injunction against Napster sets restrictions on the company's service, while both sides await the beginning of the trial, the date for which has yet to be set.

"While we are disappointed that the US Court of Appeals declined to reconsider its February decision, we recognised going in that rehearing petitions are infrequently granted," said Jonathan Schwartz, general counsel for Napster. "That is especially so at this stage of the case, where no trial has yet been held in the underlying case."

Napster can appeal Friday's decision to the US Supreme Court, although company officials said in the statement they have not decided yet how to proceed.

The injunction issued against the company has taken a toll on its service. It required Napster to institute a file blocking system to remove music files covered by copyrights owned by the music labels, publishers and song writers. Since the filtering system was put in place, use of Napster's service has dropped dramatically, according to recent figures from research firm Webnoize.

Napster has said it will move to what will effectively be a two-tiered subscription service by the third quarter. A basic service will include songs from small artists and independent record labels, while a premium service will allow users to trade songs from the major labels. Pricing hasn't been announced.