Barack Obama has announced new US sanctions against foreign banks that help Iran sell its oil, saying the new measures will raise pressure on the Islamic Republic to meet its international nuclear obligations.
The new penalties by the US president were announced on Tuesday and would target China's Bank of Kunlun and Iraq's Elaf Islamic Bank.
In a statement, Obama said the sanctions made clear that the US would expose any financial institution that assists "the increasingly desperate Iranian regime" to access the international financial system.
Obama is also extending sanctions to the purchase or acquisition of Iranian petrochemical products. The sanctions are authorised in part for those who provide support to the National Iranian Oil Company and the Central Bank of Iran.
Mark Dubowitz, head of the non-profit group Foundation for Defense of Democracies, which pushes for tough sanctions on Iran, said the penalties would help curb Iran's efforts to evade US banking and oil sanctions.
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Speaking to Al Jazeera, Jamel Abdi of the National Iranian American Council says sanctions are not having the effect intended.
He said that the country has adapted to sanctions over the past three decades, "private businesses are pushed out the economy by the sanctions and illegal enterprises, smugglers, all these enterprises that are supported and part of state actually benefit".
"When you have measures like this... in fact what the strategy is starting to become is a collective punishment to impose suffering on ordinary Iranians to put pressure on the Iranian regime," he said.
The election year announcement comes as Obama aims to show he is being tough on Iran amid criticism from Republican rival Mitt Romney.
Romney, currently on a tour of Europe that also took him to Israel, which has hinted at a military attack to rein in Iran, said on Monday the US had "a solemn duty and a moral imperative" to block Iran from achieving nuclear weapons capability.
Obama's decision, in an executive order, came in advance of congressional votes on new sanctions intended to further strip Iran of its oil-related revenues.
But Obama said the US was still committed to finding a diplomatic resolution to the deadlock but would seek "to hold the Iranian government accountable for its actions".
"If the Iranian government continues its defiance, there should be no doubt that the United States and our partners will continue to impose increasing consequences," he said.