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 providers of wireless networking solutions for large corporate customers.

Most experts predicted a second Trump administration to ease up on antitrust enforcement and be more receptive to mergers than the previous administration.

The US 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.