US data storage giant Western Digital said it is trying again to block the sale of Toshiba’s prized semiconductor business to a rival group in the heated battle with its chip venture partner.

The latest legal action by the US company, which jointly invests in Toshiba’s main chip plant, comes in the wake of Tosh’s decision last week to sell the unit to a consortium led by Bain Capital and South Korean chipmaker SK Hynix.

The $18 billion agreement with the Bain group is, however, still unsigned, with Toshiba telling its main banks this week that Apple, a member of the consortium and an important client, had yet to agree to key terms.

Western Digital’s injunction case is being played out in the International Court of Arbitration, where the California-based company, which argues no deal can be done without its consent, initiated proceedings against Toshiba earlier this year.