India is pressing ahead with energy deals with Iran despite unilateral sanctions signed in early July by U.S. President Barack Obama.
The Obama administration barred foreign entities doing business in the Iranian energy sector from U.S. markets.
Indian Foreign Secretary Nirupama Rao said after the July measure that New Delhi was "justifiably concerned" by "unilateral sanctions" that restrict investment in the Iranian energy sector by third-party countries.
P.J. Crowley, a spokesman for the U.S. State Department, said Washington was reminding its allies that "business as usual" with Iran was no longer acceptable.
"So everyone has a responsibility to do what each country can to convince Iran to change its present course (on nuclear issues,)" he said. "I'll leave it to India to describe what steps it is going to take."
India, meanwhile, is moving closer to Iran on talks for a number of options for natural gas imports.
India imports more than 18 million tons of petroleum from Iran each year, slightly less than 10 percent of its annual imports.