The US Department of Justice (DOJ) has informed Keysight Technologies that its $1.5 billion acquisition of Spirent will only be approved if it divests three of the company’s communications units to Viavi Solutions.

The Justice Department said that Keysight has to divest Spirent Communications’ high-speed ethernet testing, network security testing, and RF channel emulation businesses to resolve antitrust concerns.

Keysight announced an agreement to acquire British telecoms testing company Spirent last spring. The company outbid Viavi’s $1.3 billion purchase offer.

Shortly after the deal was announced, the antitrust division filed a civil antitrust lawsuit in the US District Court for the District of Columbia to block the proposed transaction due to concerns over competitiveness.

Keysight and Spirent account for 85 percent of the market for high-speed ethernet testing, more than 60 percent of the market for network security testing, and more than 50 percent of the market for RF channel emulators, noted the DOJ.

Customers of the two companies include chipset manufacturers, cloud computing providers, mobile network operators, government labs, and large enterprises.

“The proposed divestiture to Viavi, an established and innovative test and measurement company, ensures that American consumers and businesses will continue to benefit from competition that promotes innovation, and which allows American companies to maintain global leadership,” said Assistant Attorney General Abigail Slater of the antitrust division.

“This consent decree proceeding secures enforceable commitments from the merging parties, provides transparency into the antitrust division’s efforts to resolve merger investigations, and gives the public an opportunity to comment as provided by statute.”

The DOJ said that without its proposed divestiture, Keysight’s acquisition of Spirent “would likely result in higher prices, lower quality, and reduced innovation to the detriment of customers and American consumers.”

The three business units that will be snapped up by IT communications company Viavi, account for about 40 percent of Spirent’s total revenues. In the DOJ’s announcement this week, it also noted that it expects Viavi to hire certain key Spirent employees to support these units.