Iran's President Hassan Rouhani has vowed to "break" swingeing sanctions re-imposed by the US targeting core parts of the economy.
The Trump administration is restoring all sanctions lifted under the 2015 nuclear deal in a bid to pressure Iran. They will hit oil exports, shipping and banks, and make it difficult to do business with the oil-rich nation.
But Mr Rouhani struck a defiant tone, saying that Iran would "continue selling oil". "We will proudly break the sanctions," he said at a meeting of economic officials.
European countries which are still party to the accord designed to curb Iran's nuclear activity say they will help businesses bypass the sanctions. But there are doubts about how successful this will be.
US President Donald Trump withdrew the US from the nuclear accord earlier this year, an agreement he called the "worst deal ever negotiated". President Trump says that he wants to get Iran back to the negotiating table.
The president says his "maximum pressure" strategy is working. "[Iran] wanted to take over the whole Middle East. Right now they just want to survive," he told a rally in Tennessee, Reuters reported.