By Harshita Mary Varghese and Joey Roulette

(Reuters) -Amazon on Friday said it booked three Falcon 9 launches with Elon Musk's SpaceX to help deploy the ecommerce giant's Project Kuiper satellite network, tapping a rival in the satellite internet business for its multi-billion dollar launch campaign.

Amazon aims to build Kuiper as a constellation of 3,236 satellites in low Earth orbit to beam broadband internet globally and compete with SpaceX's Starlink network, which already has some 5,000 satellites providing nearly global coverage.

Amazon, which vowed in 2019 to invest $10 billion into the project, will put an unspecified number of Kuiper satellites on three Falcon 9 rockets from SpaceX beginning in mid-2025, the company said Friday.

The Falcon 9 missions add to 83 rocket launches it had already procured from Jeff Bezos' space company Blue Origin, the Boeing-Lockheed joint venture United Launch Alliance and Europe's Arianespace in a multi-billion dollar launch deal.

Amazon was sued by a shareholder in August for not adequately considering SpaceX as a launch provider when it was selecting most of the 83 other rides to space in late 2021 and 2022. The company said the lawsuit's claims "are completely without merit."

Cleveland Bakers and Teamsters Pension Fund, a fund that lodged the suit in a Delaware court, said in its complaint the launch contracts were the second-largest capital expenditure in Amazon's history at the time.

Amazon's largest acquisition is its $13.7 billion deal to buy Whole Foods in 2017.

Amazon's announcement that it added SpaceX rockets to its launch campaign comes just three days before its deadline to lodge a substantive defense against the shareholder lawsuit, according to a court scheduling order.

Amazon in September filed a motion to dismiss the lawsuit, saying it would detail its defense in a later briefing. On Friday, the same day as Amazon's SpaceX announcement, the court set a deadline of Dec. 4 for Amazon to outline its motion to dismiss.

SpaceX's partially reusable Falcon 9 rockets have been a crucial advantage over rivals in its rapid deployment of Starlink, a fast-growing internet network that made the Musk-owned company the world's largest satellite operator.

Eutelsat's OneWeb, another satellite internet rival, relied on Russia's Soyuz rocket for deploying the bulk of its network. But OneWeb turned to SpaceX when Russia invaded Ukraine and seized $50 million worth of the company's satellites.

U.S. regulators require Amazon to deploy half of the Kuiper network by 2026. The company launched its first two prototype satellites in orbit in October and announced successful tests last month.

Amazon expects to deploy enough satellites for "early customer pilots" in the second half of 2024. It plans to use United Launch Alliance's Atlas 5 and the yet-to-launch Vulcan rocket for the first few batches of satellites.

(Reporting by Harshita Mary Varghese and Arsheeya Bajwa in Bengaluru; Editing by Arun Koyyur and Chris Reese)