Another country that has been seeking a sanctions waiver is Turkey, which takes significant volumes via pipeline from neighboring Iran.
U.S. sanctions on Iran's oil sector are set to come into effect on November 5, after U.S. President Donald Trump pulled his country out of the 2015 Iranian nuclear deal in May.
The US aims to cripple the Iranian economy to pressure Tehran to halt its nuclear activities and what the US says is broad support for "terrorism" in the region, Pompeo said.
There are many ways to convince the U.S. that this is essential for the country.
Foad Izadi: You know, there is a serious opposition from all countries in the world basically with the exception of a couple, Israelis and Saudis, but the rest of the world is basically objecting to President Trump's policy towards Iran because what Trump is doing is actually punishing countries for implementing a United Nations resolution.
"India said to the U.S. that they can´t stop before March, they are facing a major currency crisis", explained Joel Hancock, analyst at Natixis.
The reimposition of sanctions "is aimed at depriving the regime of the revenues it uses to spread death and destruction around the world", Pompeo said.
Yemeni pro-gov't forces advance in Houthi-controlled Hodeidah despite casualties
On Tuesday it was reported that the real death toll in Yemen was likely five times higher than the official count given. UN Secretary-General Antonio Guterres on Friday called for a halt to violence to pull Yemen back from the "precipice".
A new Congressional Research Service report found the original sanctions "had a substantial effect on Iran's economy and on some major strategic decisions". Some said they're already used to them, while others chose to downplay the effect.
"Don't be disillusioned about how painful this will be", says Ellie Geranmayeh, senior policy fellow at the European Council on Foreign Relations.
The US wanted all countries to stop buying oil from Iran by November 4.
Iran said it was not troubled over the re-imposition of USA sanctions.
This is the second major batch of sanctions imposed by the administration of President Donald Trump since he pulled the United States from a landmark nuclear deal in May.
All are among Iran's biggest oil customers, and they have argued that stopping their purchases immediately would cause oil prices to spike worldwide.
As a result of the latest sanctions, he said the USA expects to have reduced Iranian crude oil exports by more than 1 million barrels even before these sanctions go into effect.
Pompeo said the U.S. would grant exemptions to eight countries that have pledged to or have already cut back on purchases of petroleum from Iran, which has long depended on crude exports to power its economy.
Most global sanctions on Iran were lifted in early 2016 under a deal Iran signed with world powers the year before under which it curbed its uranium enrichment programme, widely seen overseas as a disguised effort to develop an atomic bomb. "Iran's oil exports are decreasing and difficulties paying Iran for oil with hard currency are evident".