Compuware Corp signaled on Friday it wouldn’t yield without a fight to the US Department of Justice’s declared intention to block the number-one management and development software vendor’s acquisition of its closest rival, Viasoft Inc. Farmington Hills, Michigan-based Compuware said it had struck a deal with Viasoft to extend the deadline for Viasoft common stock holders to decide whether to accept the $9 per share offer for the company until this Friday. The offer was previously due to expire on October 29.

The DoJ served Compuware with a lawsuit on Friday contending that the deal would inflate the price of software testing and fault management software for the mainframe computer market where both firms compete. The DoJ’s action drew a stinging riposte from Compuware chairman and chief executive officer, Peter Karmanos. The DoJ has made it clear they don’t understand what our products do or the dynamics of the mission-critical software marketplace. Unfortunately they’ve compounded their error by choosing to file this lawsuit, he stormed. Karmanos said the firm has yet to decide whether to contest the case in court. We are currently in the process of reviewing our option with counsel, he added.