Jammu, April 16 -- While the latest missile and drone strikes launched by Iran against Israel have reignited calls in the US to tighten sanctions, President Joe Biden faces constraints in dramatically curbing Iran's oil exports due to worries over high energy prices and angering key trade partner China.

Iran has relied heavily on its oil exports to prop up its economy despite strict US sanctions. According to industry sources, China has emerged as the largest buyer of Iranian crude, importing over 1 million barrels daily - accounting for 90% of Iran's exports and meeting 10% of China's demand.

However, shipping data indicates much of this trade occurs under the radar through indirect routes and ship-to-ship transfers that obscure the or...