Toshiba Corp. said Wednesday it has decided to sell its chip unit to a Japan-U.S.-South Korea consortium for around ¥2.4 trillion ($21 billion), rejecting a counterbid from its longtime partner Western Digital Corp.

Toshiba made the decision at a board meeting to sell Toshiba Memory Corp. to the consortium led by U.S. fund Bain Capital that it had signed a memorandum with last week to speed up talks on the sale. Toshiba will negotiate exclusively with the group to quickly seal a deal.

Toshiba said the chip unit selloff would improve its balance sheet by some ¥740 billion, making it possible for the firm to get out of debt by the end of next March.