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.

The lawsuit said that the combination of businesses would eliminate competition, raise prices and reduce innovation.

The U.S. Department of Justice has sued to block Hewlett Packard Enterprise's $14 billion deal to acquire networking gear maker Juniper Networks, arguing that it would stifle competition, according to a complaint filed on Thursday.