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.

Hewlett Packard is set to merge with Juniper for $14 billion. However, the U.S. Justice Department is suing to block the merger.

Hewlett Packard Enterprise shares are trading lower Thursday after the U.S. Department of Justice (DOJ) filed an antitrust lawsuit to block its proposed $14 billion acquisition of Juniper Networks.