In a bid to choke Iran’s oil and shipping industries, the US slapped sanctions against the country on 5 November. However, India and seven other countries got a temporary waiver to keep buying crude from Iran.

After pulling out of the 2015 nuclear deal between Iran and five UN Security Council members plus Germany, US President Donald Trump is trying to cripple Iran’s oil-dependent economy and force Tehran to give up on its missile and nuclear programmes.

Striking a defiant note, Iranian President Hassan Rouhani said his country will continue to sell its oil despite Washington’s “economic war”. Foreign minister Mohammad Javad Zarif claimed US “bullying” was backfiring by making Washington more isolated.

The US has pledged to eventually halt all purchases of crude oil from Iran, but for now it said eight countries - India, China, South Korea, Japan, Italy, Greece, Taiwan and Turkey - can continue imports without penalty. Crude is Iran’s main export, contributing one-third of the government’s revenues.

“More than 20 importing nations have zeroed out their imports of crude oil already, taking more than 1 million barrels of crude per day off the market,” said US Secretary of State Mike Pompeo. “The regime to date since May has lost over $2.5 billion in oil revenue.”

Pompeo said the oil waivers were issued to countries that have already cut purchases of Iranian crude over the past six months, and to “ensure a well-supplied oil market”. The exceptions are designed to last 180 days.

Trump said he wanted to go slow on the sanctions so as not to cause global price spikes. “I could get the Iran oil down to zero immediately, but it would cause a shock to the market. I don’t want to lift oil prices,” he said.

Iran’s crude exports peaked at 2.8 million barrels per day (bpd) in April. Overall exports have since fallen to 1.8 million bpd, and is expected to drop further.

Oil markets have been anticipating the sanctions for months and the world’s biggest producers have been increasing output. Output from the world’s top producers - Russia, the US and Saudi Arabia - in October rose above 33 million bpd for the first time, up 10 million bpd since 2010.

The US sanctions also cover 50 Iranian banks and subsidiaries, more than 200 people and vessels in its shipping sector, national airline Iran Air and more than 65 of its aircraft.