WASHINGTON—The Justice Department on Thursday sued to block the tie-up of Hewlett Packard Enterprise and Juniper Networks, a $14 billion deal that would join the second-largest and third-largest providers of wireless networking solutions for large corporate customers.

U.S. government regulators sued to block Hewlett Packard Enterprise’s $14 billion acquisition of rival Juniper Networks on Thursday, saying the combination would eliminate competition, raise prices and reduce innovation.

Juniper Networks stock fell Thursday after the Justice Department moved to block a planned acquisition of the networking company by Hewlett Packard Enterprise.The Justice Department filed a complaint in California district court that seeks to block the merger on antitrust grounds.