The office building of health insurer Anthem is seen in Los Angeles, California February 5, 2015. REUTERS/Gus Ruelas

WASHINGTON (Reuters) - Health insurer Anthem Inc said on Tuesday that Cigna Corp could not unilaterally terminate an agreement between the two companies to merge.

“Under the terms of the merger agreement, Cigna does not have a right to terminate the agreement. Therefore, Cigna’s purported termination of the merger agreement is invalid,” Anthem said in a statement.

Cigna had said earlier on Tuesday that it would terminate the planned deal after a federal judge ruled on Feb. 8 that the deal was illegal under antitrust law.