In its drive to deprive Iran’s government of its main source of revenue, oil exports, the administration of US President Donald Trump has announced it will end exemptions from sanctions for countries still buying from Iran next month.

The  six-month waivers, granted when sanctions against the Middle East country were reimposed last year following the US exit from the 2015 Iran nuclear accord known as the Joint Comprehensive Plan of Action (JCPOA), are due to expire in May. 

According to news reports, an end to the exemptions could affect China, India, Japan, South Korea and Turkey to varying degrees.

Three of the eight countries initially granted waivers – Greece, Italy and Taiwan – have stopped importing Iranian oil. Japan now says it, too, has ended imports, but reports suggest it does not yet have a suitable alternative supplier. South Korea is said to have stopped imports earlier but recommenced buying in March.

US Secretary of State Mike Pompeo said the decision not to renew the waivers showed that the Trump administration was "dramatically accelerating” its pressure campaign against Iran “in a calibrated way that meets our national security objectives while maintaining well supplied global oil markets.”

Pompeo said Washington would “stand by its allies and partners” as they seek other sources of supply. In addition to a pledge that Saudi Arabia and the UAE would ease the transition, he said the US would increase its own production, without indicating whether it would export, or to which countries.

Iran's foreign ministry dismissed the US announcement, saying it "did not and does not attach any value or credibility to the waivers.” China, which along with India, remains a major buyer of Iranian oil, also criticized the move, insisting that the US “has no jurisdiction to interfere.”

On Twitter, Turkish foreign minister Mevlut Cavusoglu said the US move would not serve regional peace and stability and would harm the Iranian people.

According to consultancy FGE Energy, Iran’s exports have fallen to around 1 million barrels per day (bbl/d) since the US decision to reimpose sanctions last year. Before the sanctions, exports averaged about 2.5 million bbl/d.

Energy Aspects, another consultancy, told British newspaper Financial Times that the US was giving consumers a false sense of security. Not only could there be a mismatch in the number of barrels needed, but also in the different crude grades required by the market.

Other commentators said they thought the US action could boomerang, as higher oil prices – crude soared skywards on Washington’s announcement – would hurt the US as well. One report said Tehran in retaliation has now pledged to close the Strait of Hormuz, through which oil is shipped from all the major Middle Eastern supplier.