U.S. officials have expressed confidence that those who have been operating under waivers to buy Iranian oil will be able to find alternative supplies when those waivers expire next week.
Speaking to reporters on a conference call, the officials cited China, Irans biggest oil customer, as a country they say should be able to fulfill its oil needs elsewhere.
China has criticized the U.S. decision, saying Chinese business with Iranian companies is transparent and legal.
U.S. President Donald Trump reimposed sanctions on Iran last year after he abandoned the 2015 international agreement that gave Iran sanctions relief in exchange for it limiting its nuclear activity.
The sanctions are meant to pressure Tehran to change what the administration calls Irans malign activities, and so far, the Trump administration says the measures have denied the Iranian government $10 billion.
The United States issued eight waivers when it brought back the sanctions in November, temporarily exempting most of the biggest buyers of Iranian oil. Those included China, India, Japan, South Korea, Taiwan, Turkey, Italy and Greece. Since the sanctions were reintroduced, Italy, Greece and Taiwan have halted their Iranian oil imports.
Iranian President Hassan Rouhani said Wednesday his country must resist the sanctions because the Trump administration does not intend to negotiate in good faith with the Islamic republic.
The U.S. is not ready to hold negotiations at all and its measures are aimed at breaking up the Iranian nation, Rouhani said.
He added that Iran will have to make the U.S. regret its decision for which we have no choice but to resist.
Irans Supreme Leader Ayatollah Ali Khamenei said despite the U.S. actions, Iran would still be able to export our oil to the extent that we need and when we decide. He added the actions will not remain without an answer, but did not provide details.
Iranian Foreign Minister Mohammad Javad Zarif also warned the United States, saying at an Asia Society event in New York it should be prepared for the consequences if it tries to stop Iran from finding buyers of its oil and using the Strait of Hormuz to transport it.
U.S. Secretary of State Mike Pompeo justified ending the temporary waivers that were granted at a news conference Monday.
The goal remains simple: to deprive the outlaw regime of the funds it has used to destabilize the Middle East; he said.