For countries including China, India and South Korea, the deadline for new waivers is December.
Even a key proponent of sanctions said he wonders about the need to force dramatically deeper cuts.
"We've probably reached the point of diminishing returns with respect to Iran's oil exports," said Mark Dubowitz, the head of the Foundation for Defense of Democracies, who has pushed for stronger sanctions on Iran.
Dubowitz said it would take a great deal of work to cut global imports of Iranian oil much below 800,000 bpd. Lawmakers are now turning their attention to new types of sanctions that could more quickly hit Tehran's foreign reserves.
Read the full article here