The 80-page report by CRS, an independent research wing of the US Congress, said that Indian leaders have agreed to further reduce dependence on Iranian oil. Iran is India's second-largest oil supplier.
"Publicly, Indian leaders have not pledged further significant reductions but press and industry accounts say that India plans further reductions along the lines of those negotiated in early 2012 by Japan," the report said.
"Indian officials say that more drastic reductions would require significant investment to switch over refineries that handle Iranian crude, and will take time," it said.
According to the report, India has been able to use the sanctions to force concessions from Iran, including an Iranian acceptance of payment for about 45 per cent of the oil sales in rupees, Indian currency but which is not convertible.
"Rupee payments will facilitate the settlement of payments for oil in the form of barter trade. Apparently in preparation for doing increased barter trade, India sent a large trade delegation to Iran (in March) to discuss increased exports to Iran of staple goods such as sugar and wheat commodities not subject to international sanctions," it said.
"Indian officials say some of their major companies, including those of the Tata group, have ended or reduced their business with Iran," it said.