A dozen Chinese rare earth companies are planning to jointly sue Hitachi Metals Ltd. as early as next month, claiming it is holding invalid patents and exercising patent rights in an illegitimate manner, state-run media reported Tuesday.

The China Daily said each member company in the industrial alliance has paid $1.5 million to cover possible costs incurred during the legal process, which could start in early September in both the United States and China.

The newspaper said China's Ministry of Industry and Information Technology has offered to assist them.