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WASHINGTON -- The Trump administration is set to authorize the sale of unarmed surveillance drones to India, a congressional aide and industry representative said Friday, as the two nations' leaders prepare for their first face-to-face meeting.

India initiated its request to buy 22 Guardian unmanned aircraft for maritime surveillance last year. The deal is estimated to be worth about $2 billion. It is still subject to congressional approval.

A green light from the administration would mark a further deepening in defense ties as India's Prime Minister Narendra Modi meets with President Donald Trump at the White House on Monday.

Modi's two-day visit to Washington, which starts Sunday, takes place amid uncertainty over the relationship because of differences on trade and other issues.

So far in his presidency, Trump has focused on outreach to China, India's strategic rival, as he looks to Beijing to rein in North Korea. But Washington and New Delhi share concerns about China's rise as a military power.

India reportedly wants the drones for surveillance of the Indian Ocean -- waters that China's navy increasingly traverses after establishing its first overseas base in the Horn of Africa nation of Djibouti. India's archrival Pakistan would also likely be opposed to the drone sale.

A defense industry representative with knowledge of the proposed sale told The Associated Press that the administration is going to approve it. A congressional staffer familiar with the matter confirmed that information. Both sources requested anonymity as they weren't authorized to discuss the potential deal.

David McKeeby, spokesman for the State Department bureau of political-military affairs, said it does not comment on proposed defense sales before Congress is formally notified.

General Atomics, the U.S.-based manufacturer of the Guardian aircraft, said in a statement to AP: "While we can't comment on government-to-government negotiations, we are certainly standing by to provide the services we can to U.S. allies."

India does not have a formal alliance with the U.S., but defense ties have intensified in recent years with joint drills between the two militaries and defense sales. The South Asian nation, which has traditionally bought most of its defense equipment from Russia, is looking to upgrade its capabilities.

Since 2008, India has signed more than $15 billion in U.S. defense contracts, including for C-130J and C-17 transport aircraft, P-8I maritime patrol aircraft, Harpoon missiles and Apache and Chinook helicopters.

Ashley Tellis, an expert on South Asia at the Carnegie Endowment for International Peace, said the U.S. decision to offer the Guardian aircraft to India is significant as the U.S. has a standing policy of declining export of such advanced drones other than to allies involved in combined operations with U.S. forces.

"Much bureaucratic china within the U.S. government had to be broken to get to this decision," he said.

Republican Sen. John Cornyn of Texas and Democratic Sen. Mark Warner of Virginia wrote to the administration in March backing the sale, saying it served U.S. national security interests and would support thousands of U.S. manufacturing jobs. But there could still be pushback from Congress. While there is bipartisan support for closer U.S.-India security ties, some lawmakers remain wary of the export of U.S. drone technology to non-allies.

Modi, a Hindu nationalist, will be making his fourth visit to the U.S. since he took office in 2014. He forged a strong relationship with President Barack Obama, and on his last visit in June 2016, he addressed Congress and described the U.S. as an "indispensable partner."

This visit is likely to be lower key and aimed at building a personal bond with Trump. They share a populist streak and a knack for using social media, and are likely to find common ground on combating Islamic extremism. Modi will be urging a tougher stance on Pakistan over militants that India blames for attacks on its territory.

But there could be increased strains on trade issues.

India is among nations singled out by the Trump administration for their trade surpluses with the U.S., which in India's case totaled $30.8 billion in 2016. New Delhi is also closely watching the administration's review of the H1B visa program, under which thousands of skilled Indian workers come to the U.S.

New Delhi was irked by Trump's decision to pull out of the Paris climate accord. In making the announcement, the U.S. president said New Delhi had made its participation "contingent on receiving billions and billions and billions of dollars in foreign aid." India denies that and says it will continue to be part of the accord, regardless of U.S. participation.