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

Shares of both the server maker and Juniper Networks ( JNPR ) fell more than 3% in afternoon trading. The antitrust lawsuit marks the first since President Donald Trump took office last week.

The DOJ argued that the acquisition would eliminate competition and would lead to only two companies - Cisco Systems and HPE - controlling more than 70% of the U.S. market for networking equipment.

More than a year ago, the server maker said that it would buy Juniper Networks ( JNPR ) for $14 billion in an all-cash deal, as it looks to spruce up its artificial intelligence offerings.

"Juniper has also introduced innovative tools that have materially decreased the cost of operating a wireless network for many customers. This competitive pressure has forced HPE to discount its offerings and invest in its own innovation," the DOJ said in its complaint.

Juniper gained prominence over the past few years as data centers flocked to its products for use in AI applications.

Stiff competition from Juniper forced HPE to sell its products at a discount and spend to introduce new features under the "Beat Mist" campaign, named after the networking gear company's rival product, the DOJ wrote.

"Having failed to beat Mist on the merits, HPE changed tactics and in January 2024 opted to try to buy Juniper instead," the agency added.

HPE representatives met with President Trump's antitrust enforcers regarding its bid for Juniper, Bloomberg News reported earlier this week.

UK's Competition and Markets authority and the European Union have cleared the deal. HPE and Juniper did not immediately respond to requests for comment on the DOJ's complaint.