Toshiba fired another legal missive at manufacturing partner Western Digital, warning the U.S. company to stop its "harassment" as the Japanese company tries to sell its flash memory business.

Toshiba sent a letter to Western Digital's chief legal officer on Wednesday forcefully reasserting its right to auction off the business in which the two companies hold certain assets together. The letter, from Toshiba's lawyer at Morrison & Foerster, said the joint venture only owns equipment — and nothing more — and that the value of those joint assets is less than 5 percent of the Japanese company's chip business.

The Tokyo-based company wants to sell its flash memory chip spinoff to offset losses in its nuclear business and avoid having its shares delisted from the Tokyo Stock Exchange. Western Digital has sought to block the sale on concerns the operations may fall into the hands of competitors, but hasn't been able to match the price offered by other bidders. Western Digital CEO Steve Milligan plans to present a revised offer as soon as this week, a person familiar with the matter said last week.