The U.S. Justice Department will file a lawsuit as soon as this week to stop Halliburton from merging with Baker Hughes, a deal that would combine the No. 2 and No. 3 oil services companies, a source familiar with the matter said.
The two sides had been discussing asset sales aimed at saving the deal, which was announced in November 2014.
Halliburton declined comment.
(Reporting by Diane Bartz)