The United States will stop offering sanction waivers to five countries that import Iranian oil as it steps up pressure on the regime.
Japan, South Korea, Turkey, China and India continue to import oil from Iran due to an exemption granted by the United States.
The Trump administration said the sanctions waivers won't be renewed when they expire on 2 May.
The move comes on top of existing strict penalties imposed on Iran which try to choke off all the revenue the country makes from oil sales.
The White House said in a statement: "This decision is intended to bring Iran's oil exports to zero, denying the regime its principal source of revenue."
Secretary of State Mike Pompeo said there will be no grace period for those countries to comply.
He said: "We're going to zero. We're going to zero across the board.
"The goal remains simply to deprive the outlaw regime of the funds that it has used to destabilise the Middle East for decades and incentivise Iran to behave like a normal country."
In November, the US reimposed sanctions on Iranian oil exports after President Trump unilaterally pulled out of a 2015 nuclear accord between Iran and six world powers.
But Washington granted exemptions to Japan, South Korea, Taiwan, Turkey, China, India, Italy and Greece to allow limited purchases for six months.
The waivers were in place in part to give those countries time to stop buying Iranian oil but also to ease any impact on global energy markets.
Italy, Greece and Taiwan stopped importing oil from Iran while the others continued.
Mevlut Cavusoglu, the Turkish foreign minister, criticised the decision, tweeting: "Turkey rejects unilateral sanctions and impositions on how to conduct relations with neighbours."
Israeli prime minister Benjamin Netanyahu said the move "is of great importance for increasing pressure on the Iranian terrorist regime."
He added: "We stand with the United States' determination against Iranian aggression and this is the right way to stop it."
Iran's exports have fallen to less than 1 million barrels per day from more than 2.5 million before sanctions were re-imposed a year ago.
Pompeo says production increases elsewhere, with Saudi Arabia and the United Arab Emirates committing to pump more oil, will make up for the loss of Iranian oil on the market.