The US government is escalating financial sanctions against Iran and ratcheting up pressure on Iranian companies suspected of supporting Tehranâ€™s nuclear ambitions.US-Iranian relations deteriorated after the 1979 Islamic revolution, but have worsened since the US-led invasion of Iraq in 2003 and following the election of Iranian President Mahmoud Ahmadinejad two years ago.
US President George W. Bush claims Iran is racing to develop nuclear weapons, something that Tehran, which has signed the Nuclear Non-Proliferation Treaty, denies.
Iran says its nuclear programme is peaceful, although Ahmadinejad has predicted Israelâ€™s destruction.
As tensions have flared, the worldâ€™s superpower has brought its financial and economic firepower to bear on Iran, moving in part to cut off Tehranâ€™s access to the global financial system.
The US Treasury and other government agencies have blacklisted and applied asset freezes against at least 15 Iranian entities so far this year.
â€œWe believe that there is a real potential that these sanctions will have the effect of changing the government of Iranâ€™s mind about the defiant policy it is currently pursuing,â€ Stuart Levey, the treasuryâ€™s undersecretary for Terrorism and Financial Intelligence, told AFP.
The United Nations has also invoked sanctions against Iran over its refusal to halt uranium enrichment, which can be used to construct a nuclear bomb.
American companies and invididuals are barred from doing business with blacklisted Iranian firms and Washington hopes other countries will step up such actions.
Most of the Iranian entities targeted by the US this year, including the Atomic Energy Organisation and the Mesbah Energy Company, operate in the nuclear, energy and industrial industries.
But Iranâ€™s banking sector is also in Washingtonâ€™s sights, as well as Iranian groups it says fund â€œterroristâ€ organisations such as Hizbollah, the Lebanese-based Shiite political group.
The Treasury blacklisted Iranâ€™s fifth-largest state-owned bank, Bank Sepah, in January, claiming it had funded weapons proliferation, including a Chinese firmâ€™s sale of â€œmissile-related itemsâ€ to Iran in 2005.
Several Japanese banks reportedly cut ties with another Iranian bank, Bank Saderat, after it was blacklisted last September. Swiss bank UBS ceased its business activities in Iran last year.
US lawmakers are also becoming more critical of Iranâ€™s nuclear quest. But some experts are skeptical.
â€œI donâ€™t think if the assets of a few Iranian officials are frozen or if the state of California and the state of New York decide to divest from Iran, suddenly the regime will buckle and say â€˜weâ€™re going to change our nuclear approachâ€™,â€ said Karim Sadjadpour, an Iranian researcher at the Carnegie Endowment for International Peace.