Only Iraq and Saudi Arabia have the excess production capacity to offset an embargo on Iranian crude, a senior ministry official in Tehran said.
A bill passed in the United States gave the White House authority to put more pressure on the Iranian Central Bank, which would make it harder for foreign companies to pay Tehran for oil imports. The European Union has targeted more Iranian figures with sanctions but stopped short over an outright ban.
Iran, the No. 3 oil exporter in the world, said if the Europeans had other options, they would have imposed further sanctions.
"If Europeans could find an alternative for Iran's oil, they would definitely go for imposing sanctions against Iranian oil," an official at the Iranian Oil Ministry told the semiofficial Fars News Agency on condition of anonymity.
He added that excess crude from Iraq is developing but not quickly enough to meet Europe's appetite. Saudi Arabia, meanwhile, would have to address market problems in response to sanctions by addressing Asian demands.
The aim of the tightened sanctions on Iran is to punish the country for its nuclear ambitions and choke off a significant source of revenue. Critics of the sanctions note they would increase the price of oil and earn more money for the Iranian government.