Western Digital Corp. (NASDAQ:WDC) has filed a lawsuit to stop partner Toshiba Corp. (TYO:6502) from selling its chips business without its consent. Western Digital announced on Monday that it had initiated arbitration procedures with the International Chamber of Commerce. The two companies jointly operate Toshiba’s main semiconductor plant.

Western Digital is unhappy that Toshiba is planning to sell its stakes in three joint ventures along with the chip unit. It claims that Toshiba cannot transfer the joint venture’s interests into an affiliate and then sell the affiliate without its consent. Western Digital said such a move would breach the agreements over the joint ventures.

Western Digital CEO Steve Milligan said in a statement, “Seeking relief through mandatory arbitration was not our first choice in trying to resolve this matter. However, all of our other efforts to achieve a resolution to date have been unsuccessful, and so we believe legal action is now a necessary next step.” Western Digital is demanding Toshiba stop an all-out sale without consent from Western Digital unit SanDisk.

Toshiba said it had yet to be notified of any arbitration and that Western Digital had no grounds to interfere with the sale process. Toshiba argues that neither party can block a change of control by the other partner under their joint venture contract. It claims that when Western Digital acquired SanDisk, it never sought or received Toshiba’s approval.

The lawsuit could potentially derail the auction, which is needed to provide a much-needed capital injection for Toshiba. The Japanese conglomerate needs the sale to cover billions in dollars in cost overruns at its U.S. nuclear unit Westinghouse, now bankrupt. Sources say the auction of the Toshiba chip unit could fetch about 2 trillion yen ($18 billion). A legal battle could delay or end the auction.

The auction has attracted numerous suitors, including private equity firm KKR, Taiwan’s Foxconn and U.S. chipmaker Broadcom. Western Digital is among the companies trying to buy Toshiba’s chip unit. However, it put in a much lower offer for the world’s second biggest NAND chip producer than other suitors, according to a source with knowledge of the matter.

Fresh funds are urgently needed to shore up its balance sheet. Toshiba ended the financial year that ended in March with a 950 billion yen ($8.4 billion) net loss and negative shareholder equity worth 540 billion. Its auditors refused to sign off on its results for the quarter that ended in December. Toshiba said it expects to post a net profit of 50 billion yen ($441 million) for the financial year ending March 2018.