The deal follows talks that began in 2018. It is expected to significantly increase India's surveillance and intelligence capabilities and is in line with US efforts to coax India away from buying Russian military equipment and counter China's growing dominance.
India's apex defense body approved the procurement last year just before Prime Minister Narendra Modi's state visit to Washington, while the Pentagon approved it in February.
The drones will be predominantly used by the navy in the Indian Ocean Region, Reuters reported last year.
Two of India's long-time rivals, China and Pakistan, have sophisticated air defense systems that can limit the use of the drones along India's land borders.
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