The U.S. Department of Justice is preparing to sue to stopthe merger of theoil-field service firms HalliburtonCo. and Baker Hughes Inc.,according to April 5 reports by Bloomberg and Reuters.

The DOJ intends to file the suit as soon as this week toblock the combination of the world's second- and third-largest oil servicefirms. The department may havetelegraphed its moves in an April 4 lawsuit against a hedge fundwith stakes in both firms that said a merger "threatens to substantiallylessen competition in numerous markets."

Halliburton and Baker Hughes have been waiting sinceNovember 2014 for antitrust regulators to OK the $34.6 billion deal.