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- and third-largest companies providing wireless networking solutions for large corporate customers.

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.

The US Justice Department sued to block Hewlett Packard Enterprise Co.’s $14 billion acquisition of Juniper Networks Inc., arguing the tie-up would harm competition in the market for enterprise wireless equipment used by large companies,