Six Japanese and U.S. makers of DVD players have given Chinese firms in the audio equipment industry until Sunday to enter into negotiations over paying patent royalty fees for DVD production.

Hitachi Ltd. and AOL Time-Warner Inc. are among the six companies that had notified China of the deadline as of Wednesday.

Japanese company sources allege that market share valued at 500 billion yen was lost to the Chinese companies, which made and sold DVD players without paying the fees.

The six Japanese and U.S. firms have indicated their readiness to pursue legal action, including damage claims and import curbs, in the event that the Chinese firms refuse to negotiate and pay the patent fees.

Trade friction involving intellectual property rights between Japan and China will probably heat up if the Chinese side fails to respond.

Chinese production of DVD players has reached an annual volume of 10 million, 80 percent of which is exported to the United States, according to industry sources.

Last year, patent royalty fees totaling $200 million were not collected by the Japanese companies, the sources said.