The news comes weeks after Pakistan reported using a home-made drone in combat when it attacked militants on its soil, raising the prospect of a new front in the nuclear-armed neighbours' standoff over Kashmir that has twice spilled into war.
The plan to acquire Israeli Herons was first conceived three years ago, but in January the military wrote to the government asking for speedy delivery, the sources said, as Pakistan and China develop their own drone warfare capabilities.
India has already deployed Israeli unmanned aerial vehicles (UAVs) along the rugged mountains of Kashmir for surveillance, as well as on the disputed border with China, where the two armies have faced off against each other.
Earlier this month, the government approved the Air Force's request to acquire 10 Heron TP drones at an estimated Rs 2,620 crore from the state-owned Israel Aerospace Industries (IAI); these drones can be fitted with weapons to engage targets on the ground, an air force official with knowledge of the matter said.
He said he expected the agreement to be inked soon. The Indian Defence Ministry declined to comment.
"It's risky, but armed UAVs can be used for counter insurgency operations internally as well across the borders; sneak attacks on terrorist hideouts in mountainous terrain, perhaps," said an army officer in the defence planning staff.
Gurmeet Kanwal, a former head of the government-funded Centre for Land Warfare Studies in New Delhi, said the armed Herons due to enter Indian service by late 2016 will give the Air Force deep-strike capability.
The United States has carried out hundreds of drone strikes inside Pakistan, targeting al Qaeda and other militants in its northwest. Pakistan has allowed such targeted killings, even though it complains about them in public.
Indian drones, in contrast, face being shot down if they show up on Pakistani radars, the army officer and Kanwal said.
Michael Kugelman, South Asia specialist at the Washington D.C.-based Woodrow Wilson International Centre for Scholars, said the arrival of lethal drones in the region could heighten mutual suspicion at a time when ties are strained.
"Pakistan might worry that India could use an armed drone to attack terrorist safe havens in Pakistan or to target a specific terrorist there...India might worry that Pakistan will now be tempted to add drones to its repertoire of asymmetric warfare tactics it has used against India," he said.
Only the United States, Israel and Britain are known to have used armed drones in combat, although more than 70 countries have UAVs with surveillance capabilities, according to New America, a Washington DC-based think-tank.
China has no public strategy for armed drone development, but it has poured resources into UAVs and has shown them off at exhibitions. Chinese combat drones still lag far behind the Israeli-made ones in terms of capability, military experts say.
Israel does not confirm or deny using or producing armed drones. The state-owned IAI declined comment on the proposed sale of the Herons, as did Israel's Defence Ministry, which oversees such arms exports.
India has been trying to develop its own combat drone, but the defence research development organisation or DRDO has struggled to integrate a missile onto the proposed Rustom series of UAVs.
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