US President Donald Trump has decided to end exemptions from sanctions for countries still buying oil from Iran, the BBC reports.
The White House said waivers for China, India, Japan, South Korea and Turkey would expire in early May, after which they could face economic penalties.
Saudi Arabia and others in OPEC will more than make up the Oil Flow difference in our now Full Sanctions on Iranian Oil. Iran is being given VERY BAD advice by @JohnKerry and people who helped him lead the U.S. into the very bad Iran Nuclear Deal. Big violation of Logan Act?— Donald J. Trump (@realDonaldTrump) April 22, 2019
Mr Trump reinstated the sanctions last year after abandoning a nuclear deal between Iran and six world powers.
In November, the US reimposed sanctions on Iran's energy, ship building, shipping, and banking sectors, which officials called "the core areas" of its economy.
However, six-month waivers from economic penalties were granted to the eight main buyers of Iranian crude - China, India, Japan, South Korea, Taiwan, Turkey, Italy and Greece - to give them time to find alternative sources and avoid causing a shock to global oil markets.
Three of the eight buyers - Greece, Italy and Taiwan - have stopped importing Iranian oil. But the others had reportedly asked for their waivers to be extended.