President Barack Obama said late on Thursday he had extended sanctions against Iran imposed in 1995 as it continued to pose an "extraordinary threat" to the U.S. national security and foreign policy.
The sanctions prohibit U.S. companies from doing trade, export/import and investment with Iran and from helping the development of its oil industry.
They were imposed by the Clinton administration in 1995 and have been extended on an annual basis by successive presidents. They would have expired without Obama's formal action to extend them.
“The actions and policies of the Government of Iran are contrary to the interests of the United States in the region and pose a continuing unusual and extraordinary threat to the national security, foreign policy, and economy of the United States,” Obama said in a message to the Congress.
“For these reasons, I have determined that it is necessary to continue the national emergency declared with respect to Iran and maintain in force comprehensive sanctions against Iran to respond to this threat,” he added.
Meanwhile, Iranian President Mahmoud Ahmadinejad dismissed on Friday the sanctions as a "childish idea" as he officially launched a natural gas project in the Gulf, Iranian media reported.
Ahmadinejad said the idea of creating obstacles for Iran's development with sanctions was "a childish idea and a big mistake," the official IRNA news agency reported.
"Of course our belief is that with the grace of God the Iranian nation can traverse the course of development," he said.
He described Friday's commissioning of Phases 9 and 10 of the South Pars field, Iran's single biggest natural gas deposit, as a "happy gift" for the Iranian nation, which is also the world's fourth-largest oil producer.
"This grand achievement happened under conditions in which some in the world with immorality and misbehavior did not fulfill their promises," Ahmadinejad said.
"They signed contracts to provide equipment and spare parts but ... some of the equipment and spare parts remained aboard ship and were taken back,” he said in an apparent reference to Western firms scaling down their investment plans in Iran.
The sanctions are one portion of the large range of punitive U.S., United Nations and international measures imposed against Iran, for various reasons, including its alleged backing for terrorism and nuclear drive.
Over more than 20 years, Washington has steadily increased sanctions against Iranian interests in hopes of pressuring Tehran to pull back on its nuclear program—which the U.S. says is aimed at developing nuclear weapons.
The United States says Iran must also halt its alleged support for groups Washington has labeled "terrorist," including Lebanon's Hezbollah and armed Palestinian groups.
Iran also faces UN Security Council sanctions over its refusal to freeze uranium enrichment activities, but over the past five years has pressed on with its controversial nuclear work.
In a change of policy from the Bush administration, Obama has said he would be open to engaging with Iran on a range of issues, from its nuclear ambitions to how it could help in Afghanistan, where NATO-led forces are struggling against a worsening insurgency.
The Obama administration intends to invite Tehran to an international conference on Afghanistan, which borders Iran, planned for this month. Iran has said it is prepared to consider the invitation.
That was a clear shift from previous president George W. Bush, who rejected talks unless Iran halted uranium enrichment, the process which makes fuel for nuclear power plants but can also be used to produce the core of an atomic bomb.
Obama has said the United States is prepared to extend a hand of peace to Iran if it "unclenched its fist". Iranian President Mahmoud Ahmadinejad said he is open to talks with Washington but demanded a fundamental change to U.S. policy in the Middle East.
The United States cut off diplomatic ties with Iran during the 1979-81 hostage crisis, in which a group of militant Iranian students held 52 U.S. diplomats hostage at the American embassy for 444 days.