Kroger Co. is fighting back against a lawsuit brought by Albertsons Cos. over its failed $24.6 billion takeover of the rival grocery chain, escalating a dispute that began after US antitrust enforcers succeeded in blocking the deal last year.

U.S. grocery chain Kroger countersued Albertsons on Tuesday, escalating a legal battle between the companies following the collapse of their proposed $25 billion merger in December.

Albertsons and Kroger spent over two years and more than $850 million on an unsuccessful effort to merge. The two supermarket giants are now spending additional money fighting over the fallout. Kroger filed a countersuit Tuesday against Albertsons over the bitter end to its planned acquisition of the Boise-based grocery chain.