German and French consumer groups have joined a Nordic-led drive to force Apple Inc. to make its iTunes online store compatible with digital music players made by rival companies, a Norwegian official said Monday.

Currently, song purchased and downloaded through iTunes are designed to work with Apple's market-leading iPod players but not competitors' models, including those using Microsoft Corp.'s Windows Media system. Likewise, iPods generally can't play copy-protected music sold through non-Apple stores.

Last June, consumer agencies in Norway, Denmark and Sweden claimed that Apple was violating contract and copyright laws in their countries.

Norwegian Consumer Ombudsman Bjoern Erik Thon said French consumer lobby UFC-Que Choisir and its German counterpart, Verbraucherzentralen, joined the effort late last year, and other European countries are considering it. Finland's Kuluttajavirasto consumer group is also part of the effort.

"This is important because Germany and France are European giants," Thon said. "Germany, in particular, is a big market for digital music."

The Nordic regulators have met Apple officials at least twice on the complaints.

In a written statement after one such meeting in Oslo in September, Apple said it "is working to address the concerns we've heard from several agencies in Europe, and we hope to resolve these issues as quickly as possible."

Thon said Norway gave Apple until September to change its polices, or face possible legal action and fines in the country.

"It cannot be good for the music industry for them to lock music into one system," he said.

A French law that allows regulators to force Apple to make its iPod player and iTunes store compatible with rival offerings went into effect in August.