There is a palpable fear in New Delhi that the new U.S. president's lack of focus on India, and limited appointment of South Asia focused advisors, has resulted in India falling off the radar in Washington," Eurasia Group's Shailesh Kumar and Sasha Riser-Kositsky said in a note.
Defense deals, however, are one area where the two countries could make progress because of bipartisan support, an Indian official involved in the preparations for the visit said.
The two sides have stepped up efforts in recent weeks to get inter-agency clearance for the sale of the Guardian drone, made by California-based General Atomics.
India has raised the issue of the drones with the Pentagon three times since June 2016, officials said.
U.S. Senators John Cornyn and Mark Warner wrote in March to Defense Secretary James Mattis and Secretary of State Rex Tillerson saying the Guardian deal, estimated at more than $2 billion, would advance U.S. national security interests and protect U.S. jobs.
An industry official involved in promoting India-U.S. business ties said the drone sale enjoyed support from the White House and Congress, and was now awaiting clearance from the State Department.
While the Guardian drones that India is pushing for are unarmed, the Indian military had originally asked for missile-firing Predator Avenger aircraft, a request turned down by the Obama administration.
Sources say there is some concern in the State Department that if India were to get the surveillance drones New Delhi would renew its push to acquire armed drones, which its military has eyed ever since they were deployed by U.S. forces against militants in Pakistan.
U.S. export laws typically prohibit the transfer of such arms to a country unless it is fighting alongside U.S. forces.
India and the United States will also discuss the sale of U.S. fighter jets during Modi's trip, in what could be the biggest deal since they began deepening defense ties more than a decade ago.
On Monday, Lockheed Martin announced an agreement with India's Tata Advanced Systems to produce F-16 planes in India, provided it won a contract to equip the Indian Air Force with hundreds of new aircraft.
Lockheed has offered to shift its ageing F-16 production line from Fort Worth, Texas as part of Modi's "Make-in-India" drive while it ramps up production of the high-end F-35 aircraft at home.
Since Trump's election on an "American First" platform, U.S. and Indian officials have sought to play down any contradiction between his stated desire to protect American jobs and Modi's "Make in India" policy, arguing, for example, that deals in which components made in the United States are shipped to India for assembly benefit workers in both countries.