Toshiba Corp has told Western Digital Corp not to interfere with the sale of its prized chip unit, disputing claims by the U.S. firm that it had breached a joint venture contract.

Western Digital, which is a partner in Toshiba's main semiconductor plant as well as one of the bidders for the chip business, has argued that the Japanese firm is violating their contract by transferring their joint venture's rights to the newly formed unit.

In a May 3 letter sent by Toshiba's lawyers, the Japanese conglomerate disputed Western Digital's argument and said it would pursue all available remedies if it saw continued interference in the sale process.

Western Digital's "campaign constitutes intentional interference with Toshiba's prospective economic advantage and current contracts. It is improper, and it must stop," the letter, which was seen by Reuters, said.

In a separate letter, also dated May 3, the general manager of Toshiba's legal affairs accused Western Digital of failing to sign some joint venture agreements.

If Western Digital refuses to sign by May 15, the chip unit would protect its intellectual property rights by suspending Western Digital employees' access to all of the unit's facilities, networks, and databases, the letter said.

A Western Digital spokeswoman in Japan declined to make an immediate comment.