New Delhi, Sept. 20 -- There is "guarded optimism" that the US will eventually bring down the 50% tariff on exports from India, a senior official in New Delhi has said, citing the visit by a US trade negotiating team and sustained diplomatic signals from President Donald Trump, including his birthday call to PM Narendra Modi. The official said New Delhi has adopted a carefully calibrated approach of "neither provoking, nor complying" with US pressure. P9...